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IC 


8924 



Bureau of Mines Information Circular/1983 




Updated Process Flowsheets 

for Manganese Nodule Processing 



By Benjamin W. Haynes, Stephen L. Law, 
and Riki Maeda 




UNITED STATES DEPARTMENT OF THE INTERIOR 



fC^ !*!*'• ^MUM^Jl^^ 



Information Circular; 8924 

w 



Updated Process Flowsheets 

for Manganese Nodule Processing 



By Benjamin W. Haynes, Stephen L. Law, 
and Riki Maeda 




UNITED STATES DEPARTMENT OF THE INTERIOR 
James G. Watt, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 



As the Nation's principal conservation agency, the Department of the Interior 
has responsibility for most of our nationally owned public lands and natural 
resources. This includes fostering the wisest use of our land and water re- 
sources, protecting our fish and wildlife, preserving the environmental and 
cultural values of our national parks and historical places, and providing for 
the enjoyment of life through outdoOT recreation. The Department assesses 
our energy and mineral resources and works to assure that their development is 
in the best interests of all our people. The Department also has a major re- 
sponsibility for American Indian reservation communities and for people who 
live in Island Territories under U.S. administration. 






This publication has been cataloged as follows: 



Haynes, Benjamin W 

Updated process flowsheets for manganese nodule processing. 

(Information circular ; 8924) 

Bibliography: p. 11 

Includes index. 

Supt. of Docs, no.: I 28.27:8924. 

1. Manganese— Metallurgy. 2. Manganese nodules. 1. Law, 
Stephen L, 11. Maeda, Riki, III. Title. IV. Series: Information circu- 
lar (United States. Bureau of Mines) ; 8924. 

TN295.U4 [TN799.1V13] 622s [669'.732] 82-600368 



For sale by the Superintendent of Documents, U.S. Gorernment Printing Office 
Washington, D.C. 20402 



<» CONTENTS 

Page Page 

^ Abstract 1 Detailed process descriptions 10 

-7 Introduction 2 Major assumptions 10 

"y Acknowledgments 2 Materials handling 10 

Manganese nodule processing overview 2 Summary 10 

Generic types of processes 2 References 11 

Processes most likely for first-generation commercial 

use 3 Appendix A. — Gas reduction and ammoniacal leach 

Summary process descriptions 3 process 12 

Gas reduction and ammoniacal leach process 3 Appendix B.—Cuprion ammoniacal leach process 28 

Cuprion ammoniacal leach process 5 Appendix C— High-temperature and high-pressure 

High-temperature and high-pressure H2SO4 leach H2SO4 leach process 44 

process 6 Appendix D. — Reduction and HCI leach process 62 

Reduction and HCI leach process 7 Appendix E.— Smelting and H2SO4 leach process 79 

Smelting and H2SO4 leach process 8 



ILLUSTRATIONS 

1. Gas reduction and ammoniacal leach process 4 

2. Cuprion ammoniacal leach process 5 

3. High-temperature and high-pressure H2SO4 leach process 6 

4. Reduction and HCI leach process 7 

5. Smelting and H2SO4 leach process 9 

A-1. Key to symbols 16 

A-2. Ore processing and drying 17 

A-3. Reduction 18 

A-4. Leaching-aeration 19 

A-5. Solid-liquid separation 20 

A-6. Liquid ion exchange-extraction 21 

A-7. Cobalt stripping-organic purge 22 

A-8. Liquid ion exchange-stripping 23 

A-9. Copper electrowinning — commercial 24 

A-10. Nickel electrowinning — commercial 25 

A-11. Cobalt recovery 26 

A-1 2. Ammonia recovery 27 

B-1. Key to symbols 32 

B-2. Ore preparation 33 

B-3. Reduction-leach 34 

B-4. Oxidation-leach 35 

B-5. Solid-liquid separation 36 

B-6. Liquid ion exchange-extraction 37 

B-7. Cobalt stripping-organic purge 38 

B-8. Liquid ion exchange-stripping 39 

B-9. Copper electrowinning — commercial 40 

B-10. Nickel electrowinning- -commercial 41 

B-11. Cobalt recovery 42 

B-1 2. Ammonia recovery 43 

C-1. Key to symbols 48 

C-2. Ore processing 49 

C-3. Leaching 50 

C-4. Solid-liquid separation 51 

C-5. Pregnant liquor pH adjustment 52' 

C-6. Copper liquid ion exchange 53 

C-7. Cobalt stripping-organic purge 54 

C-8. Copper electrowinning — commercial 55 

C-9. Copper raffinate pH adjustment 56 

C-10. Nickel liquid ion exchange-extraction 57 

C-11. Nickel liquid ion exchange-stripping 58 

C-1 2. Nickel electrowinning — commercial 59 

C-1 3. Cobalt recovery 60 

C-1 4. Ammonia recovery 61 



ILLUSTRATIONS— Continued 

Page 

D-1. Key to symbols 66 

D-2. Ore processing and drying 67 

D-3. Hydrochlorination 68 

D-4. Leaching and washing 69 

D-5. Copper liquid ion exchange 70 

D-6. Copper electrowinning — commerical 71 

D-7. pH adjustment and cobalt extraction 72 

D-8. Nickel liquid ion exchange 73 

D-9. Nickel electrowinning — commerical 74 

D-10. Manganese recovery 75 

D-11. Cobalt recovery 76 

D-12. HCI recovery 77 

D-1 3. Waste recovery 78 

E-1. Key to symbols 84 

E-2. Ore preparation and drying 85 

E-3. Reduction 86 

E-4. Smelting 87 

E-5. Converting 88 

E-6. Ferromanganese reduction 89 

E-7. Matte leaching 90 

E-8. pH adjustment 91 

E-9. Copper liquid ion exchange 92 

E-10. Cobalt stripping-organic purge 93 

E-11. Copper electrowinning — commercial 94 

E-1 2. Copper raffinate neutralization 95 

E-1 3. Nickel liquid ion exchange-extraction 96 

E-1 4. Nickel liquid ion exchange-stripping 97 

E-1 5. Nickel electrowinning — commercial 98 

E-1 6. Cobalt recovery 99 

E-1 7. Ammonia recovery 100 



TABLES 

A-1. Operating parameters for gas reduction and ammoniacal leach process 13 

B-1. Operating parameters for Cuprion ammoniacal leach process 29 

C-1. Operating parameters for high-temperature and high-pressure H2SO4 leach process 45 

D-1. Operating parameters for reduction and HCI leach process 63 

E-1. Operating parameters for smelting and H2SO4 leach process 80 



UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 

pet percent 

psi pound per square inch 

psig pound per square inch, gage 

tpd ton per day 

tpy ton per year 



A/m^ 

atm 

°C 

gpi 

hr 


ampere per square meter 

atmosphere 

degree Centigrade 

gram per liter 

hour 


in 


inch 


kg 

lb 


kilogram 
pound 



UPDATED PROCESS FLOWSHEETS FOR 
MANGANESE NODULE PROCESSING 



By Benjamin W. Haynes,^ Stephen L. Law,^ and Riki Maeda^ 



ABSTRACT 



The Bureau of Mines, in cooperation with the National Oceanic and Atmospheric Adminis- 
tration (NOAA), has updated a 1977 NOAA report prepared by Dames & Moore entitled, 
"Description of Manganese Nodule Processing Activities for Environmental Studies." This 
updated report contains detailed flowsheets and descriptions of the five potential first- 
generation nodule recovery schemes now considered most likely to be used by industry; 
they are high-temperature gas reduction and ammoniacal leach, Cuprion ammoniacal 
leach, high-temperature and high-pressure H2SO4 leach, reduction and HCI leach, and 
smelting and H2SO4 leach. The first three processes are three-metal recovery schemes (Cu, 
Ni, and Co) with the option of Mn recovery from the tailings. The remaining two processes are 
four-metal (Cu, Ni, Co, and Mn) recovery schemes. 

All except the HCI process are assumed to use a nodule feed rate of 3 million tons per 
year (dry basis). Final metal products are Co powder and cathode Cu and Ni. A minor 
amount of Ni is also recovered as powder, and some Cu and Zn are recovered as mixed 
sulfides. Manganese in the four-metal processes is recovered as either manganese metal or 
ferromanganese. 

^Supervisory research chemist, Avondale Research Center, Bureau of Mines, Avondale, Md. 
^Research supervisor, Avondale Research Center, Bureau of Mines, Avondale, Md.. 
^Chemical engineer, Avondale Research Center, Bureau of Mines, Avondale, Md. 



INTRODUCTION 



This report is one in a series of reports issued by the Bureau 
of Mines as part of a research project entitled, "Analysis and 
Characterization of Potential Manganese Nodule Processing 
Rejects." Deep seabed mining for manganese nodules, includ- 
ing the processing of nodules to recover value metals, raises a 
variety of environmental, social, and economic considerations. 
To address the waste management aspects of the recovery of 
value metals from nodules, the National Oceanic and Atmo- 
spheric Administration (NOAA), U.S. Department of Commerce, 
the Environmental Protection Agency (EPA), and the Bureau 
of Mines and the Fish and Wildlife Service, U.S. Department of 
the Interior, after consultation with affected and concerned 
interests, have agreed to embark on a multiyear cooperative 
research program that has the following overall objective: 

"To provide information needed by Federal and State 
agencies in preparation for receipt of industry's commer- 
cial waste management plans." 

The NOAA-funded research conducted by the Bureau of 
Mines has the objective of obtaining a first-order chemical and 
physical characterization of reject waste materials (tailings) 
from the types of manganese nodule processing techniques 
representative of those being developed by industry. The 
result of this research is expected to be a technical report that 
can be used by (1) environmental scientists in subsequent 
research to assess the potential effects of waste management 
alternatives, and (2) regulatory agencies in the determination 
of what standards and test requirements must be met. This is 
expected to facilitate the development of a basic framework 
that accommodates the desire to assure protection of the 
environment and the development of a new minerals process- 
ing industry. 

In order to adequately assess the potential effects of dispos- 
ing of reject waste materials from manganese nodule processing, 
appropriate process flowsheets must be developed so that the 
processes representative of first-generation nodule process- 
ing plants can be simulated and waste can be generated in the 
laboratory. 



During August 1977, NOAA published a report prepared 
under contract by Dames & Moore entitled "Description of 
Manganese Nodule Processing Activities for Environmental 
Studies" (7)^ This report considered five different processing 
techniques or "roadmaps" (flowsheets). Three of these five, 
designed to produce Cu, Ni, and Co as primary products, are 
called "three-metal plants" and two are "four-metal plants" 
designed to produce manganese as a fourth primary product. 
It should be noted that three-metal plants could be designed to 
produce some manganese if market conditions are favorable. 
The processing techniques identified in the NOAA report are 
as follows: 

1 . Gas reduction and ammoniacal leach process. 

2. Cuprion ammoniacal leach process. 

3. High-temperature and high-pressure H2SO4 leach proc- 
ess. 

4. Reduction and HCI leach process. 

5. Smelting and H2SO4 leach process. 

This Bureau of Mines report has taken the Dames & Moore 
1 977 flowsheets and used the input from industrial and other 
concerned parties to update the report and present, where 
necessary, changes and modifications in the flowsheets. 

The flowsheets presented in this report are adaptations of 
the original flowsheets presented in reference 7. Only minor 
changes have been made in the sections common to all 
flowsheets. All flowsheets, however, are presented for 
completeness. This report, unlike the 1 977 study, contains no 
energy balance or material balance figures. These flowsheets 
were used to design, construct, and operate bench-scale sys- 
tems to generate reject waste materials. Reject waste materi- 
als are being generated and will be characterized to determine 
chemical and physical parameters important to future environ- 
mental and economic considerations. The results of the char- 
acterizations will be published in a separate report. 



ACKNOWLEDGEMENTS 



The authors wish to acknowledge Francis C. Brown, of F. C. 
Brown Associates, Inc., for providing copies of the original 
flowsheets and for manuscript review. Also the technical staffs 
of Ocean Minerals Co., Ocean Mining Associates, Ocean Man- 



agement Inc., and Kennecott Minerals Co. are acknowledged 
for manuscript reviews. Their assistance has been invaluable 
in updating the 1977 Dames & Moore and EIC Laboratories 
report. 



MANGANESE NODULE PROCESSING OVERVIEW 



GENERIC TYPES OF PROCESSES 

In the work performed by Dames & Moore in 1 977 (7), a 
literature search revealed several methods for recovering the 
valued metals (Mn, Ni, Co, Cu) from manganese nodules 
using pyrometallurgical and hydrometallurgical processes, or 
combinations of the two. Furthermore, the extraction tech- 
niques can be classified by the type of lixiviant used to solubi- 
lize the metals of interest. These lixiviant types are ammonia-. 



chloride-, and sulfate- based. Using this format. Dames & Moore 
outlines 1 2 potential routes to metals recovery. These routes 
are 

Ammoniacal systems 
1 . Gas reduction and ammoniacal leach 



"Italicized numbers in parentheses refer to items in the list of references 
preceding the appendixes. 



2. Cuprion ammoniacal leach 

3. High-temperature ammonia leach 
Chloride systems 

1 . Reduction and HCI leach 

2. Hydrogen chloride reduction roast and acid leach 

3. Segregation roast 

4. Molten salt chlorination 
Sulfate systems 

1 . High-temperature and high-pressure H2SO4 leach 

2. Smelting and H2SO4 leach 

3. H2SO4 reduction leach 

4. Reduction roast and H2SO4 leach 

5. Sulfation roast 

Ammoniacal systems are used in processing of land-based 
nickeliferous laterites which are, in some respects, similar to 
manganese nodules. It is well known that Cu, Ni, and Co are 
soluble in ammoniacal ammonium carbonate (Caron process) 
and ammonium sulfate solutions. These processing routes 
involve selective reduction of the metals from their oxide states 
and disruption of the manganese nodule matrix to permit 
rapid, complete dissolution of the valuable metals. 

Acid chloride solutions are also capable of solubilizing the 
metal values of interest including manganese, and a substan- 
tial body of literature exists describing process conditions for 
nodule reduction and metals recovery, separation, and 
purification. 

Copper, nickel, and cobalt are also soluble in strong acid 
sulfate systems and serve as the initial step for various possi- 
ble process routes. The high-temperature H2SO4 leach proc- 
ess technology is used in recovering nickel from laterites, 
where the high temperature increases the rates of the dissolu- 
tion of Cu, Ni, and Co, and limits the solubility of undesirable 
compounds such as Fe and Mn. Alternative routes involving 
the acid sulfate lixiviant system include the selective, high- 
temperature reduction of the nodules, separation of manganese- 
rich slags from the metallic phases, sulfidation of metallic 
phases, and subsequent selective leaching of the sulfide 
materials. A ferromanganese product could also be recovered 
by further selective reduction of the manganese-rich slag phases. 



PROCESSES MOST LIKELY FOR 
FIRST-GENERATION COMMERCIAL USE 

Of the 12 generic process types presented previously, 7 



have sufficient technical problems to preclude the likelihood of 
commercial development. Flowsheets have been developed 
for the five process options that are considered as first-generation 
choices, both from the published literature and by analogy to 
the processing of land-based ores (7). These five process 
options are as follows: 

1. Gas reduction and ammoniacal leach. 

2. Cuprion ammoniacal leach. 

3. High-temperature and high-pressure H2SO4 acid leach. 

4. Reduction and HCI leach. 

5. Smelting and H2SO4 leach. 

The five processes can be broken down into three-metal 
and four-metal recovery systems with the three-metal sys- 
tems having an option to recover manganese from the tailings. 
The basic three-metal systems are (1) gas reduction and 
ammoniacal leach process, (2) Cuprion ammoniacal leach 
process, and (3) high-temperature and high-pressure H2SO4 
leach process. The remaining two are considered four-metal 



The recovery of manganese from the tailings of the three- 
metal systems involves two basic types of treatment. For the 
ammoniacal leach tailings, manganese can be recovered to a 
limited extent by the flotation of MnCOa. The f^/lnCOa could 
then be further processed to produce a manganese oxide 
product and sold as such or further processed to produce 
ferromanganese or other manganese alloys. 

The residue from the H2SO4 system would require dissolu- 
tion of the tailings and subsequent chemical manipulation to 
recover the manganese as Mn02 or another form. The oxide 
product could be separated and sold or further processed to 
make ferromanganese or other manganese alloys. The possi- 
ble direct use of the tailings from either the ammonia-based 
systems or the H2SO4 system as a feed for ferromanganese 
production would require some purification of the tailings. 
Trace metals levels as well as sulfur and possibly phosphorus 
levels would be too high for direct processing of the tailings by 
conventional methods. 

For the purpose of this report, the add-on options to produce 
manganese products (ferromanganese, silicomanganese, and/or 
other oxide products) from the three-metal systems will be 
presented briefly with no process outlines. The proposed descrip- 
tions serve only as choices from several possible alternatives 
and, implementation or sehous consideration would be depen- 
dent on many conditions in addition to technical feasibility. 



SUMMARY PROCESS DESCRIPTIONS 



This section contains brief descriptions of each of the five 
processes as mentioned in the preceding section along with 
block diagrams for each process. Detailed process deschp- 
tions of each process are given in the appendixes. 

GAS REDUCTION AND 
AMMONIACAL LEACH PROCESS 

Copper, nickel, and cobalt can be recovered from nodules 
by a process involving carbon monoxide gas reduction fol- 
lowed by an ammoniacal leach process. A simplified block 
diagram for this process is shown in figure 1 . 

The first step in this process is the high-temperature (625° 
C) reduction of manganese dioxide (Mn02), the major com- 



pound in nodules, to manganese oxide (MnO) by a carbon 
monoxide-rich producer gas. The effect of this reduction is to 
disrupt the mineral structure and release the contained metals. 
The metal values solubilized are dissolved from the reduced 
nodules with a strong aqueous solution of ammonia (10 pet) 
and carbon dioxide (5 pet), at low temperature (40° C) and 
atmospheric pressure. 

The metal-bearing solution is decanted from the nodules 
and treated with a series of organic extraction steps, which 
selectively remove the copper and nickel from the aqueous 
solution. The metal values are selectively stripped from the 
organic extract with acidified aqueous solutions. The metal 
products, copper and nickel, are produced from these acidic 
solutions by electrowinning. 

Cobalt is then recovered from the aqueous ammonia-carbon 



•^""l""' carbon dioxide- 


Nickel 

f 




Copper 

f 


Cobalt 








t 


Electro- 
winning 


-| 


p 


Electro- 
winning 








Grinding and 
drying 




Chemical 
reduction 












































Nickel 
stripping 


J 


L 


Copper 
stripping 


^ 






Leach 


























































Nickel-copper 
liquid ion 
exchange 






Cobalt 
recovery 






















Waste 
containment 




Liquid-solid 
separation 








Metal-bearing 
solution 




1 




f 

Hvdroaen sulfide 






















Ammonia 
recovery 








Makeup 








IMakeup 


1 


ammonia 































Figure 1. — Gas reduction and ammoniacal leach process. 



dioxide solution by contacting it with hydrogen sulfide, which 
precipitates the insoluble sulfides of Co as well as small amounts 
of residual Cu, Ni, Zn, and other metals not removed in previ- 
ous steps. The solids are removed from the aqueous ammonia- 
carbon dioxide solution and contacted with air and hot (1 00° C) 
H2SO4 to selectively redissolve the cobalt and the small amount 
of nickel present. The undissolved sulfides are sold as minor 
products, and the cobalt and nickel are recovered from solu- 
tion in powder form by selective reduction with hydrogen at 
high pressure (34 atm) and temperature (185° C). 

The nodule residue, from which the major portion (98 pet) of 
the soluble metals has been removed, is contacted with steam 
(at 120° 0, 2 atm) to remove residual ammonia and carbon 
dioxide. The ammonia-carbon dioxide-steam mixture is con- 
densed and, together with the aqueous ammonia-carbon diox- 
ide mixture from which cobalt was removed, is recycled to 
extract more metal values from freshly reduced nodules. The 
^eam-stripped nodule residues may be combined with smaller 
amounts of other process solid and liquid wastes and sent to 
containment. 

The high-temperature reduction of nodules with simulated 
producer gases and subsequent extraction of metals with 
ammonia-carbon dioxide solutions is basically the same 
approach £is is currently used in recovering nickel from laterites 



by the Caron process, and can be considered a variation of 
currently available technology. The metal separation and puri- 
fication scheme, however, is specific to nodules and is compli- 
cated by the chemical similarity of Cu, Ni, and Co. 

Separation and purification of copper and nickel by selec- 
tive extraction with organic compounds (liquid ion exchange 
reagents) is currently practiced in the extractive metallurgy of 
copper and nickel. However, in these cases the aqueous 
solutions contain primarily one metal, the others being treated 
as impurities, not products. 

Cobalt recovery from precipitated mixtures of nickel and 
cobalt sulfides derived from laterites is also currently practiced. 
The details of the procedures used to purify the leach solutions 
prior to reduction, however, would differ somewhat from those 
used for nodules because of the differences in amount and 
content of impurities. 

Plant services include facilities for generating the producer 
gas used in nodule reduction, raising the necessary steam 
and part of the power required for process use, supplying the 
makeup and cooling water required, and providing for materi- 
als handling for process materials and supplies. The genera- 
tion of producer gases from coal or oil for the reduction of 
nodules and all other plant services represent the utilization of 
known technology essentially without adaptation. 



CUPRION AMMONIACAL LEACH PROCESS 

Copper, nickel, and cobalt can be recovered from nodules 
by the Cuprion process employing a reducing ammoniacal 
leach. A simplified block diagram of this process is shown in 
figure 2. 

The first step in this process is a low-temperature (50° C) 
hydrometallurgical reduction of manganese dioxide (MnOa), 
the major compound in nodules, to manganese oxide (MnO) 
by an aqueous ammoniacal solution containing an excess of 
cuprous ions (Cu*). The effect of this reduction is to disrupt 
the mineral structure and release the contained metals. The 
metal values are solubilized from the reduced nodules with a 
strong aqueous solution of ammonia and carbon dioxide at 
low temperature and pressure. 

The metal-bearing solution is decanted from the nodules 
and treated with a series of organic extraction steps that 
selectively remove the copper and nickel from the aqueous 
solution. The metal values are in turn selectively stripped from 
the organic extract with acidified aqueous solutions. The metal 
products, cathode copper and nickel, are produced from these 
acidic solutions by electrowinning. 

Cobalt is then recovered from the aqueous ammonia-carbon 
dioxide solution by precipitation with hydrogen sulfide, which 
also precipitates small amounts of residual Cu, Ni, Zn, and 
other metals not removed in previous steps. The solids are 



removed from the aqueous ammonia-carbon dioxide solution 
and contacted with air and hot (100° C) H2SO4 to selectively 
redissolve the cobalt and small amount of nickel present. The 
undissolved sulfides are sold as minor products, and the cobalt 
and nickel are recovered from solution in powder form by 
selective reduction with hydrogen at high pressure (34 atm) 
and temperature (185° C). 

The nodule residue, which has the major portion (98 pet) of 
the soluble value metals removed, is contacted with steam (at 
120° C, 2 atm pressure) to remove residual ammonia and 
carbon dioxide. The aqueous ammonia-carbon dioxide mixture, 
from which cobalt was removed, is also steam stripped to 
recover a high-strength ammonia solution for recycle to the 
reduction step and to provide fresh wash solution for recycle to 
extract more metal values from freshly reduced nodules. The 
steam-stripped nodule residues may be combined with smaller 
amounts of other process solid and liquid wastes and sent to 
containment. 

The hydrometallurgical reduction of nodules in an ammoniacal- 
ammonium carbonate solution has been disclosed in the patent 
literature. While this approach differs from the pyrometallurgi- 
cal reductions used in the well-known Caron process for recovering 
nickel from laterites, the basic outline for the Cuprion process 
is similar. The metal separation and purification scheme, 
however, is specific to nodules and is complicated by the 
chemical similarity of Cu, Ni, and Co. 



Nodules 



Nickel 



Copper 



Cobalt 









t 








1 












oaroon monoxiae 

1 


Electro- 
winning 




Electro- 
winning 








Grinding 




Chemical 
reduction 






































Soli 


ition 








4 


Nickel 
stripping 


♦ 




Copper 
stripping 


- 






recycle 


Leaching- 

reduced pulp 

preparation 


























































' 






Nickel-copper 
liquid ion 
exchange 






Cobalt 
recovery 






















Waste 
containment 




Leaching- 
liquid-solid 
separation 








Metal-bearing 






solution 




M 


t 
























Ammonia 
recovery 








MakeuF 
water 


) ^ 






Make 
amm( 


up 
)n 


a 































Figure 2. — Cuprion ammoniacal leach process. 



Separation and purification of copper and nickel by selec- 
tive extraction with organic compounds (liquid ion exchange 
reagents) is currently practiced in the extractive metallurgy of 
copper and nicl<el. However, in these cases the aqueous 
solutions contain primarily one metal, the others being treated 
as impurities, not products. 

Cobalt recovery from precipitated mixtures of nickel and 
cobalt sulfides derived from laterites is also currently practiced. 
The details of the procedure used to purify the leach solutions 
prior to cobalt recovery will differ somewhat from those used 
for nodules because of the differences in amount and content 
of impurities. Also, the requirement that the nodule reduction 
and wash steps be carried out with solutions of differing ammo- 
nia and ammonium carbonate compositions requires an addi- 
tional step, raffinate stripping, not used in the pyrometallurgical 
reduction-ammoniacal leach process. 

Plant services include facilities for generating the carbon 
monoxide gas used in nodule reduction, raising the necessary 
steam and power required for process use, supplying the 
makeup and cooling water required, and providing for materi- 
als-handling for process materials and supplies. The genera- 
tion of carbon monoxide gas from coal or oil for the reduction of 
cupric ion (Cu^*) and all other plant services represent the 
utilization of known technology essentially without adaptation. 



HIGH-TEMPERATURE 

AND HIGH-PRESSURE 

H2SO4 LEACH PROCESS 

Nickel, copper, and cobalt can be recovered from nodules at 
high temperatures and high pressures in an aqueous H2SO4 
solution. A simplified block diagram of this process is shown in 
figure 3. 

The first step in this process is a high-temperature (245° C) 
and high-pressure (35 atm) treatment of the ground nodules. 
Most of the major metals of value in the nodules (except 
manganese) become dissolved in the hot, strong (30 pet) 
sulfuric acid solution. Iron is not solubilized to any appreciable 
extent. After cooling, the nodule residue and acid solution are 
separated by decantation. Water is used to wash the residue 
free of acid and soluble metals and it is then combined with the 
acid solution; the residue is sent to a containment area. 

The metal-bearing acid solution passes to a pH-adjustment 
step prior to copper and nickel extraction. Copper and nickel 
are then removed from the solution with an organic extractant. 
The extracted nickel and copper are separately and selec- 
tively stripped from their respective organic extracts and trans- 
ferred to acidified aqueous solutions, which accumulate nickel 
and copper sulfate, respectively. The metal products, cathode 



Grinding 



Leaching 



Nodules 



Water 
Sulfuric acid 



Copper 

__1 



Electro- 
winning 



pH 
I adjustment 



Liquid-solid 
separation 



Copper 
liquid ion 
exchange 



Nickel Cobalts 

_i 



Electro- 
winning 



Neutralization 



Nickel W 
liquid ion 
exchange 



Waste 
containment 



Ammonia 
recovery 



Lime 



Makeup Makeup 
ammonia water 



Cobalt 
recovery 



Hydrogen sulfide 
Figure 3.— High-temperature and high-pressure H2SO4 leach process. 



nickel and copper, are produced from these acidic solutions by 
electrowinning. 

Cobalt is then recovered by precipitation with hydrogen 
sulfide, which also precipitates small amounts of residual Cu, 
Ni, Zn, and other metals not removed in the previous steps. 
The solid residue is removed from solution and contacted with 
air and hot (1 00° C) H2SO4 to selectively redissolve the cobalt 
and the small amount of nickel present. The undissolved 
sulfides are sold as minor products, and the cobalt and nickel 
are recovered from solution in powder form by selective metal 
reduction through use of hydrogen gas at high pressure (34 
atm) and temperature (185° C). 

The solution, depleted of Cu, Ni, and Co, is chemically 
treated to recover the ammonia introduced during the neutral- 
ization step. The recovered ammonia is recycled for use in the 
process, and the ammonia-free solution is returned to wash 
freshly leached nodules. 

Descriptions of high-temperature and high-pressure acid 
treatment of nodules have had limited exposure in the literature, 
with most descriptions occurring in foreign patents and papers. 
A basically similar process for treatment of nickel laterite ores 
has been used at Moa Bay, Cuba. The configuration proposed 
is an update using currently available technology of Moa Bay 
operations. The metal separation and purification scheme. 



however, is specific to nodules and is complicated by the chemi- 
cal similarity of Cu, Ni, and Co. 

Separation and purification of copper and nickel by selec- 
tive extraction with organic compounds (liquid ion exchange 
reagents) is currently practiced in the extractive metallurgy of 
nickel and copper. However, in these cases the aqueous 
solutions contain primarily one metal, the others being treated 
as impurities, not products. 

Cobalt recovery from precipitated mixtures of nickel and 
cobalt reduction differ somewhat from those used for nodules 
because of the differences in amount and content of impurities. 

Plant services include facilities for generating the necessary 
steam and part of the power required for process use, for 
supplying the makeup and cooling water required, and for 
providing materials handling for process materials and supplies. 
The generation of steam and all other plant services represent 
the utilization of known technology essentially without adaptation. 



REDUCTION AND HCI LEACH PROCESS 

Copper, nickel, cobalt, and manganese can be recovered 
from nodules by a reduction and HCI leach process. A simpli- 
fied block diagram of the process is shown in figure 4. 



Grinding 

and 

drying 



Nodules 



Hydro- 

chlorination- 

reduction 



Hydrolysis 



Hydrochloric _^ 
acid 



Water 



Hydrochloric 

acid 

chlorine 

recovery 



Water 
storage 



Leach 
liquid-solid 
separation 



Waste 
containment 



1 [ 



Copper 
liquid ion 
exchange 



Cobalt 
liquid ion 
exchange 



Nickel 
liquid ion 
exchange 



Evaporation- 
crystallization 



Electro- 
winning 



Copper 



-I Hydrogen sulfide 



Cobalt 
recovery 



Electro- 
winning 



Cobalt 



Nickel 



Fused 

salt 

electrolysis 



Manganese 



Figure 4.— Reduction and HCI leach process. 



The chemical basis of the HCI process is the reduction of the 
manganese dioxide nodule matrix with hydrogen chloride to 
yield soluble manganese chloride, thereby releasing the Ni, 
Cu, and Co for dissolution. A portion of the hydrogen chloride 
is oxidized to chlorine, and the unreacted hydrogen chloride is 
separated from the accompanying chlorine and water vapor 
for recycling. Separation is accomplished by absorption of 
gasous HCI in concentrated HCI, in which chlorine has very 
limited solubility. The remaining chlorine gas is dried by pas- 
sage through concentrated H2SO4. 

Extensive solubilization of the iron content of the nodules 
during the initial high-temperature (500° C) reaction with gas- 
eous hydrogen chloride is prevented by injection of steam. 
This results in the conversion (hydrolysis) of the iron chloride 
produced in the initial step to insoluble iron (ferric) hydroxide, 
simplifying subsequent metals separation and minimizing HCI 
regeneration requirements. In the next step, the soluble metal 
chlorides, particularly those of Mn, Ni, Cu, and Co, are brought 
into solution with water and aqueous HCI. In this process, as 
distinct from the other nodule treatment processes, the major 
metals separation steps are carried out from the chloride 
solution. 

In the base-case process, copper is selectively extracted 
from the pregnant leach liquor by contact with an organic liquid 
ion exchange reagent. After separation of the copper-loaded 
organic phase from the copper-depleted aqueous chloride 
solution, the copper is stripped into a strong H2SO4 solution. 
The resulting copper sulfate solution is sent to electrowinning, 
producing cathode copper for sale and a partially copper- 
depleted, strong H2SO4 "spent" electrolyte that is returned to 
the liquid ion exchange circuit to strip more copper. 

The chloride leach solution from which the copper has been 
removed is neutralized and passed to a solvent extraction 
step, where a different organic liquid ion exchange reagent 
selectively removes the cobalt from solution. The cobalt is 
recovered in a sequence of steps that includes stripping from 
the organic solvent, hydrogen sulfide precipitation as cobalt 
sulfide, selective leaching, and hydrogen reduction to cobalt 
powder. 

The copper- and cobalt-depleted solution is next sent to a 
liquid ion exchange circuit where nickel is selectively sepa- 
rated from the solution and stripped into an acidic sulfate 
solution for nickel electrowinning. The nickel separation has 
many features in common with copper separation, except that 
much lower acid concentrations are appropriate in the case of 
nickel. 

Of the several options for manganese recovery from nodules, 
that selected for the base-case process in this report involves 
drying of the final aqueous chloride solution to produce a dry, 
impure manganese chloride. The manganese chloride is charged 
to a high-temperature electrolysis furnace, where it dissolves 
in a molten alkali chloride bath. Electrolysis of the bath liber- 
ates molten manganese, which is tapped from the furnace, 
cast into molds, and sold as manganese metal. Fused salt 
impurities are skimmed off, solidified, and sent to waste disposal. 

The second major product of the electrolysis is chlorine gas, 
which would be recovered along with the chlorine produced in 
the initial hydrochlorination step. The recovered chlorine needs 
to be reconverted to hydrogen chloride or otherwise utilized 
offsite in a large-scale chemical process, such as the manufac- 
ture of polyvinyl chloride. 

Plant services include facilities for raising the necessary 
steam and part of the power required for process use, supply- 
ing the makeup and cooling water required, and providing for 
materials handling for process materials and supplies. The 



generation of steam and all other plant services represent the 
utilization of known technology essentially without adaptation. 



SMELTING AND 
H2SO4 LEACH PROCESS 

Copper, nickel, cobalt, and a ferromanganese alloy, if 
desired, can be recovered from nodules by a smelting and 
H2SO4 leach process. A simplified block diagram of this pro- 
cess is shown in figure 5. 

The nodules are first dried by direct contact with combustion 
gases to remove water not chemically bound to the minerals. 
The manganese dioxide and ferric oxide are then reduced to 
manganous and ferrous oxides by contact, in the presence of 
coal, with a carlDon monoxide-rich producer gas at high tempera- 
ture (>625° C up to 1 ,000° C). The hot, reduced nodules are 
then charged to an electric furnace, along with the coke and 
silica. In this step most of the Cu, Ni, Co, and Fe and some of 
the Mn are reduced (at 1 ,425° C) and form a molten alloy 
phase, which separates by gravity from the unreduced manga- 
nese slag. 

The hot alloy is transferred to converter vessels where, with 
additional silica, the manganese and most of the iron are 
re-oxidized with air, separated as a slag, and returned to the 
electric furnace. Gypsum and coke or possibly sulfur are then 
added to the alloy, producing a metal sulfide "matte" phase 
that contains the Cu, Ni, and Co. A second liquid-liquid separa- 
tion is made in the converter, with the slag returned to the 
electric furnace and the matte granulated by quenching it in 
cold water. 

The electric furnace manganese slag, with recycled iron- 
rich slags, may be further reduced (at 1 ,480° C) with additional 
coke in an electric furnace to produce a molten ferromanga- 
nese alloy, which separates by gravity from the unreduced 
manganese slag. The ferromanganese is cast for sale, and 
the waste slag is granulated for disposal. 

The metals are recovered from the granulated matte by 
dissolution into strong (5 pet), hot (110° C) H2SO4 solution in 
the presence of oxygen (at 10 atm pressure). The metal- 
bearing solution is treated by a series of purification steps in 
which it is contacted with an organic extractant that selectively 
removes the copper and nickel from the aqueous solution. 
Ammonia is added to the solution to control the pH during the 
separations. The metal values are, in turn, selectively removed 
from the organic extract and transferred to acidified aqueous 
solutions, which accumulate copper and nickel sulfates. The 
metal products, cathode copper and nickel, are produced from 
these acidic solutions by electrowinning. 

Cobalt and small amounts of copper, nickel, and other met- 
als not removed in previous steps are recovered from the 
aqueous ammonium sulfate solutions by hydrogen sulfide 
precipitation. The solids are removed from the aqueous ammo- 
nium sulfate solution and contacted with air and hot (100° C) 
H2SO4 to selectively redissolve the cobalt and the small amount 
of nickel present. The undissolved sulfides are sold as minor 
products, and the cobalt and nickel are recovered from solu- 
tion in powder form by selective reduction with hydrogen at 
high pressure (34 atm) and temperature (185° C). 

Lime is then added to the metal-free ammonium sulfate 
solution, and the mixture is contacted with steam (at 120° C, 2 
atm) to recover ammonia for reuse in the process. The gyp- 
sum formed in this step is combined with other process solid 
and liquid wastes and sent to containment. 

While detailed design information on the process implica- 



Reducing gas 










Chemical 
reduction 




Grinding and 
drying 


Nodules 














Electric 
furnace 
smelting 




Ferro- 

manganese 

reduction 


^Ferromanganese Cobalt^ 






Gypsum 


gen 








Copper 

t 




Nickel 

t 




Oxidizing 
sulfiding 




Waste 
treatment 






Electro- 
winning 








Electro- 
winning 


-1 




































PH 
adjustment 






Copper 
liquid ion 
exchange 






Neutralization 






Nickel 
liquid ion 
exchange 






1 












Leaching- 
llquid-solid 
separation 
















1 










1 










1 
















t 




Ammonia 
recovery 


* 


Cobalt 
recovery 












Waste 






c 


ontainment 






k 
Hydrogen sulfide 



Figure 5.— Smelting and H2SO4 leach process. 



tions involved in the smelting of nodules has not been published, 
enough is known about the thermodynamics of the system to 
permit a process outline to be constructed. Electric furnace 
smelting is a well developed technology, and copper and 
nickel are currently recovered by treatment of mattes formed 
during the smelting of sulfide ores. Ferromanganese of high 
purity is currently produced directly from high-quality ores. 
Thus, the reductive smelting of nodules to ferromanganese 
with subsequent sulfidizing of the alloy phase to form a matte 
is a synthesis of technologies from different areas of extractive 
metallurgy. Detailed information on slag properties (particularly 
viscosity-composition-temperature relationships); the efficien- 
cies of materials (coke, gypsum); energy consumption; and 
the distribution of minor metals and impurities among dust, 
slag, and matte phases under smelting conditions for this 
system, however, is lacking. 

The oxidative dissolution of sulfide ores and mattes is well 
known, but the metal separation and purification schemes are 
specific to nodules and are complicated by the chemical simi- 
larity of Cu, Ni, and Co. Separation and purification of copper 



and nickel by selective extraction with organic compounds 
(liquid ion exchange reagents) is currently practiced in the 
extractive metallurgy of copper and nickel. However, in these 
cases the aqueous solutions contain primarily one metal, the 
others being treated as impurities, not products. 

Cobalt recovery from precipitated mixtures of nickel and 
cobalt sulfides derived from laterites is also currently practiced. 
The details of the procedures used to purify the leach solutions 
prior to reduction will differ somewhat from those used for 
nodules because of the difference in amount and content of 
impurities. 

Plant services include facilities for generating the producer 
gas used in nodule reduction, generating the necessary steam 
and part of the power required for process use, supplying the 
makeup and cooling water required, and providing for materi- 
als handling for process materials and supplies. The genera- 
tion of producer gases from coal (or oil) for the reduction of 
nodules and all other plant services represent the utilization of 
known technology essentially without adaptation. 



10 



DETAILED PROCESS DESCRIPTIONS 



Each of the five processes are presented in detail, in the 
appendixes, with flowsheets for each unit operation. Many 
sections of the processes are similiar or identical but flowsheets 
are presented to preserve the process continuity. Major assump- 
tions used in calculating operating parameters are presented 
to show major changes from the Dames & Moore 1 977 report 
(7). Materials handling for all processes is similar and is 
presented prior to the detailed process descriptions without 
flowsheets. Plant services are presented without flowsheets 
for each of the five processes. 

MAJOR 
ASSUMPTIONS 

Certain assumptions were used in the original Dames & 
Moore report and are used in updating the process flowsheets 
in this report. The three three-metal processes and the smelting 
process are assumed to operate on a 3-million-tpy feed rate 
(dry basis). The four-metal HCI process is assumed to operate 
at 1 million tpy (dry basis). The final products are assumed to 
be Cu and Ni cathodes, some Ni powder, Co powder, small 
amounts of Cu and Zn sulfides, Mn metal, and ferromanganese. 
No energy balances or material balances are made in this 
report. 

Several significant changes from the Dames & Moore report 
are detailed here. In the 1977 Dames & Moore study (7), a 
moisture content of 37.5 pet was used as the water value of 
nodules fed to the processing plant. This value represents 
essentially the water content of as-mined nodules. Consider- 
ing the porosity of nodules (60 pet), it is likely that a substantial 
amount of water will be removed during transport from the 
mine site. Ships currently in use equipped with a Marconoflo- 
type^ dewatering system should be able to dewater the nodules. 
A recent report described the use of such a system in transport- 
ing slurried coal (30). 

A more reasonable value for moisture content of nodules 
received at the port facilities may be 1 5 to 20 pet. This fact 
would decrease the size of several components of the materi- 
als handling section, and lower the energy cost for drying the 
nodules. For this report a moisture content of 20 pet is used for 
nodules fed to the plant. This lowers the 3-million-tpy (dry- 
basis) plant feed rate from 12,500 to 10,900 tpd, and the 



1-million-tpy (dry-basis) plant feed rate from 3,750 to 3,640 
tpd. 

A second major change from the 1977 study (7) is the 
increase in size of the smelting plant from 1 million tpy (dry 
basis) to 3 million tpy (dry-basis) to allow use of conventionally 
sized furnaces. Also, particle size of the nodule feed is increased 
to minus 65 mesh instead of minus 200 or minus 325 mesh as 
previously used. 

The previous study contained an extensive bibliography 
and it will not be duplicated in this report. However, certain 
pertinent publications since 1 977 are included in the reference 
section of this report (7-6, 8-29, 31-32). Certain publications 
apply directly to one or two processes, while others are more 
general in nature. Updated details of the Cuprion process (1-3, 
20, 26) and modifications of the Caron process (5, 9-12, 
24-25, 32) have been published. Several articles on different 
aspects of H2SO4 leaching of laterites and nodules (6, 8, 10, 
18, 23) are available as well as those dealing with smelting 
processes (13, 21-22, 29, 31-32). Several review articles have 
also been published (4, 14, 17, 27-28). 



MATERIALS HANDLING 

Facilities are provided within the plant for receiving and 
reclaiming raw nodules, coal, lime and limestone, ammonia, 
other process materials, and fuel. Provisions for handling 
hydrogen chloride and chlorine are also required for the reduc- 
tion and HCI process, and provisions for handling silica, gypsum, 
and acids are made for the smelting and H2SO4 process. In the 
1977 Dames & Moore study (7), the proposed method of 
nodule transport from the port facilities was a slurry pipeline. 
Assuming nodules can be dewatered to 1 5 to 20 pet moisture, 
the use of slurry pipelines may not be cost effective. At this 
moisture content, the use of conveyors for transport appears 
more likely. Conveyors are routinely used in mining industries 
to transport materials over both long and short distances in 
many areas. The use of conveyors for nodule transport would 
involve known technology with little adaptation. Because all 
processes (except Cuprion) require the water associated with 
nodules to be completely removed, the use of dewatering 
during ship transport, coupled with conveyor transport, should 
result in an overall net energy savings. 



SUMMARY 



This report is an update of the 1 977 study (7) by Dames & 
Moore and EIC Corporation entitled, "Description of Manga- 
nese Nodule Processing Activities for Enviromental Studies," 
but does not include the energy and material balances con- 
tained in the initial study. The flowsheets presented in the 
appendixes of this report are adaptations of those in the previ- 
ous report with the changes since 1977. The five manganese 
nodule processing options outlined in this report are gas reduc- 
tion and ammoniacal leach process, Cuprion ammonical leach 
process, high-temperature and high-pressure H2SO4 leach 
process, reduction and HCI leach process, and smelting and 



^Reference to specific trade names or equipment does not imply endorse- 
ment by the Bureau of Mines. 



H2SO4 leach process. The first three processes are designed 
to recover three metals (Cu, Co, and Ni), and the latter two are 
designed to recover four metals (Cu, Co, Ni, and Mn). The 
three-metal processes have the option of recovering manganese 
from the tailings if economically feasible. 

This report differs from the 1 977 study (7) by using a larger 
mesh size of minus 65 for the feed material for all processes 
except smelting (where minimal size reduction is required); by 
using a moisture content of 20 pet rather than 37.5 pet for the 
feed nodules; by upgrading the smelting process to a 3-million- 
tpy nodule feed rate (dry basis) to allow for more convention- 
ally sized furnaces; and by recognizing the use of dewatering 
of the nodules during ship transport, coupled with conveyors 
instead of slurry pipeline transport of nodules from the port to the 
plant. 



A summary table of operating parameters is presented for 
each of tfie five processes and each process is brol<en down 
into basic unit operations (e.g., grinding, leaching, solid-liquid 
separation, solvent extraction, electrowinning, etc.). Each pro- 



cess may be examined as a complete package, containing 
detailed flowsheets and process descriptions pertaining to that 
process, even though portions of one process may be identi- 
cal to similiar segments of other processes. 



REFERENCES 



1 . Agarwal, J. C, H. E. Barrier, N. Beecher, D. S. Davies, and R. N. 
Kust. The Development of the Cuprion Process for Ocean Nodules. 
Kennecott Copper Corp., Information Center, Lexington, Mass., 1978, 
21 pp. 

2. . Kennecott Process for Recovery of Copper, Nickel, 

Cobalt, and Molybdenum From Ocean Nodules. Min. Eng., v. 31, 
1979. pp. 1704-1707. 

3. Aganwal, J. C, N. Beecher, D. S. Davies, G. L. Hubred, V. K. 
Kakaria, and H. J. Moslen. Comparative Economics of Recovery of 
Metals From Ocean Nodules. Marine Min., v. 2 (1 -2), 1 979, pp. 119-1 49. 

4. Boln, U. Limits and Possibilities of Deep Sea Mining for the 
Extraction of Mineral Raw Materials— The Case of Manganese Nodules. 
Min. Mag., January 1980, pp. 43-47. 

5. Canterford, J. H. Mineralogical Aspects of the Extractive Metal- 

■ lurgy of Nickeliferous Laterites. Proc. Australasian Inst, of Min. and 
Met., North Queensland, Australia, September 1978, pp. 361-370. 

6. Carlson, E. T., and C. S. Simons. Pressure Leaching of Nickelif- 
erous Laterites With Sulfuric Acid. Extractive Metallurgy of Copper, 
Nickel, and Cobalt, ed. by P. Queneau. Interscience Publishers, Inc., 
New York, 1961, pp. 363-397. 

7. Dames & Moore and EIC Corporation. Description of Manga- 
nese Nodule Processing Activities for Environmental Studies, Vol. III. 
Processing Systems Technical Analysis, U.S. Dept. of Commerce- 
NOAA, Office of Marine Minerals, Rockville, Md., 1977, 540 pp.; NTIS 
PB 27491 5. 

8. Duyvesteyn, W. P. C, G. R. Wicker, and R. E. Doane. An 
Omnivorous Process for Laterite Deposits. Proc. Internal. Laterite 
Symp., New Orleans, La., Feb. 19-21, 1979. Society of Mining Engi- 
neers of AIME, New York, 1979, pp. 553-570. 

9. Ek, C, J. Frenay, and J-C. Herman. Oxidized Copper Phase 
Precipitation in Ammoniacal Leaching — ^The Influence of Ammonium 
Salt Additions. Hydrometallurgy, v. 8, 1982, pp. 17-26. 

10. Evans, D. J. I., R. S. Shoemaker, and H. Veltman (eds.). Proc. 
Internal. Laterite Symp., NewOrieans, La., Feb. 19-21, 1979. Society 
of Mining Engineers of AIME, New York, 1979, 688 pp. 

1 1 . Graaf, J. E. The Treatment of Lateritic Nickel Ores— A Further 
Study of the Caron Process and Other Possible Improvements— Part 

I. Effect of Reduction Conditons. Hydrometallurgy, v. 5, 1979, pp. 
47-65. 

1 2. The Treatment of Lateritic Nickel Ores — A Further 

Study of the Caron Process and Other Possible Improvements — Part 

II. Leaching Studies. Hydrometallurgy, v. 5, 1980, pp. 255-271. 

■ 13. Halbach, P., K. Koch, H-J. Renner, and K-H. Ujma. Pyrometal- 
lurgical Processing of Manganese Nodules and Lateritic Nickel Ores 
Using Waste Materials as Reducing Agents. Erzmetall, v. 30, 1977, 
pp. 458-464. 

14. Han, K. N., and D. W. Fuerstenau. Extraction Behavior of Metal 
Elements From Deep-Sea Manganese Nodules in Reducing Media. 
Marine Min., v. 2, 1980, pp. 155-169. 

1 5. Kinetics of the Extraction of Metals From Deep-Sea 

Manganese Nodules: Part I. The Pore Diffusion Controlling Case. 
Met. Trans. B, v. 7B, 1976, pp. 679-685. 

16. Kinetics of the Extraction of Metals From Deep-Sea 

Manganese Nodules: Part II. Pore Diffusion With Chemical Reactions. 
Met. Trans. B, v. 7B, 1976, pp. 687-692. 

17. Hubred, G. L. Manganese Nodule Extractive Metallurgy Review 
1973-1978. Marine Min., v. 2, 1980, pp. 191-212. 

18. Jha, M., G. A. Meyer, and G. R. Wicker. An Improved Process 



for Precipitating Nickel Sulfide From Acidic Laterite Leach Liquors. J. 
Metals, November 1981, pp. 48-53. 

19. Khalafalla, S. E., and J. E. Pahlman. Selective Extraction of 
Metals From Pacific Sea Nodules With Dissolved Sulfur Dioxide. 
BuMines Rl 8518, 1981, 26 pp. 

20. King, D. E. C, and D. W. Pasho. A Generalized Estimating 
Model for the Kennecott Joint Venture, Manganese Nodule Process- 
ing Facility. Canada Department of Energy, Mines and Resources, 
Ottawa, Ontario, December 1979, 38 pp. 

21 . A Generalized Estimating Model for the Ocean Man- 
agement, Inc., Manganese Nodule Processing Facility. Canada Depart- 
ment of Energy, Mines and Resources, Ottawa, Ontario, December 
1979,53 pp. 

22. Montanteme, J., A. Greffe, F. Grandjacques. Selective Reduc- 
tion of Nickel Ore With a Low Nickel Content (assigned to Societe 
Francaise d'Electrometallurgie, Paris, France) U.S. Pat. 4,073,641 , 
Feb. 14, 1978. 

23. Neuschutz, D., V. Scheffler, and H. JunghanB. Verfahren Zur 
Aufarbeitung von Manganknollen Durch Schwefelsaure Drucklaugung. 
(Method for the Processing of Manganese Nodules by Sulfuric Acid 
Pressure Leaching.) Erzmetall, v. 30(2), 1977, pp. 61-67. 

24. Nilsen, D. N., R. E. Siemens, and S. C. Rhoads. Solvent 
Extraction of Nickel and Copper From Laterite-Ammoniacal Leach 
Liquors. BuMines Rl 8605, 1982, 29 pp. 

25. Osseo-Asare, K., and D. W. Fuerstenau. Adsorption Losses in 
Ammonia Leaching of Copper, Nickel, and Cobalt From Deep-Sea 
Manganese Nodules. Proc. Internal. Symp Complex Metallurgy 78, 
Bad Harzburg, W. Germany, Sept. 20-22, 1978, ed. by M. J. Jones, 
The Institution of Mining and Metallurgy, Federal Republic of Germany, 
1978, pp. 43-48. 

26. Pemsler, J. P., and J. K. Litchfield. Steam Stripping of Ammoni- 
acal Solutions and Simultaneous Loading of Metal Values by Organic 
Acids (assigned to Kennecott Copper Corporation, New York) U.S. 
Pat. 4,005,173, Jan. 25, 1977. 

27. Ritcey, G. M. DOOM Deep Ocean Mining Study— Review of 
the State of the Art of Processing Manganese Nodules. Canada 
Department of Energy, Mines and Resources, Ottawa, Ontario, Min- 
eral Science Laboratories Report MRP/MSL 76-1 15, February 1976, 
27 pp. 

28. Ritcey, G. M., B. H. Lucas, and D. J. MacKennon. DOOM Deep 
Ocean Mining Study — A Review and Comparisons of Routes for 
Processing Manganese Nodules. Canada Department of Energy, 
Mines and Resources, Ottawa, Ontario, Mineral Sciences Labora- 
tories Report MRP/MSL 77-194, February 1977, 32 pp. 

29. Septier, L., F. Dubrous, and M. Demango. Process for the 
Treatment of Complex Metal Ores Containing, in Particular, Manga- 
nese and Copper, Such as Oceanic Nodules (assigned to Societe 
Francaise d'Electrometallurigie, Paris, France) U.S. Pat. 4,162,916, 
July 31, 1979. 

30. Sims, W. N. Slurried Coal-Storage, Reclaiming, and Ship 
Loadings. Pres. at 111th AIME Ann. Meeting, Dallas, Tex., Feb. 
14-18, 1982, SME Preprint 81-144, 56 pp. 

31 . Sridhar, R., J. S. Warner, and M. C. E. Bell. Non-Ferrous Metal 
Recovery From Deep Sea Nodules (assigned to The International 
Nickel Company, Inc., Del.) U.S. Pat. 4,049,438, Sept. 20, 1977. 

32. Wilder, T. C, J. J. Andreola, and W. E. Galin. Reduction Pro- 
cesses for Manganese Nodules Using Fuel Oil. J. Metals, v. 33, March 
1981, pp. 64-69. 



12 



APPENDIX A.— GAS REDUCTION AND AMMONIACAL LEACH PROCESS 



The gas reduction and ammoniacal leach process is a three- 
metal process in which Cu, Ni, and Co are liberated by an 
oxidizing ammoniacal-ammonium carbonate leach following 
the high-temperature reduction of manganese dioxide by a 
synthesis gas. Copper and nickel are coextracted by liquid ion 
exchange (LIX) reagents and are selectively stripped and 
recovered as electrowon cathodes. Cobalt is separated from 
the raffinate by precipitation with hydrogen sulfide and is recov- 
ered from the sulfide precipitate along with some Ni, Zn, and 
Cu, by selective leaching and hydrogen reduction. The metal- 
free raffinate is recycled to provide leach liquor and to wash 
the process tailings. Ammonia and ammonium carbonate are 
recovered from leach tailings by steam stripping. 

Detailed descriptions of each segment of the process are 
given for the following flowsheets. A summary of operating 
parameters for each section is given in table A-1 . A key to the 
flowsheet symbols is given in figure A-1 . 



ORE PROCESSING AND DRYING (FIG. A-2) 

Wet nodules are reclaimed from storage and fed through a 
primary cage mill where they are reduced to minus Vs in. They 
then pass to a fluid bed dryer where surface and pore water is 
removed at 175° C by direct contact drying with combustion 
gases. Bed overflow is reduced to minus 65 mesh in a second- 
ary cage mill, and dryer and mill fines are removed from 
offgases with cyclones and an electrostatic precipitator. Offgases 
pass to gas treatment for scrubbing, while dried nodules are 
transferred hot in a covered conveyor to reduction. 



washing in a countercurrent decantation (CCD) circuit using 
covered thickeners. Wash liquor consists of recovered ammo- 
nia and ammonium carbonate along with raffinate from cobalt 
recovery. Washed tailings pass to stripping for ammonia and 
ammonium carbonate recovery while the wash overflow passes 
to leaching. 



LIQUID ION EXCHANGE- 
EXTRACTION (FIG. A-6) 

Pregnant liquor from leaching is filtered and passed to a 
three-stage, countercurrent LIX extraction circuit where copper, 
nickel, and some ammonia are removed from the pregnant 
liquor. Most of the ammonia is removed from the organic 
phase by washing with a weak aqueous ammonia solution. 
This ammonia is recovered by steam stripping a portion of the 
scrub solution, with the vapors passing to the ammonia recov- 
ery section. Provision is made for periodically cleaning the 
mixer-settler units used in extraction and stripping and for 
recovering organic and aqueous phases for recycle. Degraded 
organic, dust, and other forms of "crud" are removed from the 
organic and incinerated. Because a small amount of Co is 
coextracted and is not stripped with Cu and Ni, it must be 
removed from the LIX reagent to prevent its buildup. This is 
accomplished by precipitating the cobalt, with hydrogen sulfide, 
from a purge stream of organic. The precipitated solids are 
washed from the organic and pass to cobalt recovery, while 
the purified organic is returned to the extraction circuit (fig. 
A-7). 



REDUCTION (FIG. A-3) 

Dried nodules are reduced at 625° C in a two-stage fluid bed 
reduction roaster by contact with producer gas derived from 
coal gasification. At reduction conditions, MnOj as well as Cu, 
Co, Ni, Fe, and Zn are reduced. The carbon dioxide-rich 
offgases are cooled in waste heat recovery and used to car- 
bonate the reduced manganese oxide, forming manganese 
carbonate in a fluid bed cooler at 1 25° C. The reduced, carbon- 
ated material is further cooled by a water spray in the fluid bed 
unit and quenched with recycle liquor in an agitated tank. 
Cooled offgases pass to dust removal and unutilized carbon 
monoxide and hydrogen pass to the main boilers for combustion. 



LEACHING-AERATION (FIG. A-4) 

The reduced nodule slurry passes to a countercurrent oxidiz- 
ing leach where air is sparged into the leach slurry to oxidize 
Co^' to Co^* and Fe^* to Fe^* precipitating the Fe as insolu- 
ble ferric hydroxide in the manganese carbonate tailings. Liquid- 
solid separations are made in thickeners, which also provide 
residence time for leaching. Offgases from aeration pass to 
ammonia recovery, leached nodules to washing, and preg- 
nant liquor to LIX for metal separation and purification. 



SOLID-LIQUID SEPARATION (FIG. A-5) 

Metal values that have been solubilized and absorbed on 
the tailings in leaching are recovered from the tailings by 



LIQUID ION EXCHANGE- 
STRIPPING (FIG. A-8) 

The remainder of the ammonia is removed from the loaded 
organic by washing with a slightly acidic ammonium sulfate 
solution. The ammonium sulfate formed in scrubbing is purged 
to ammonia recovery. Nickel is selectively stripped from the 
organic by countercurrent contact at controlled pH with depleted 
electrolyte from nickel electrowinning. Because electrowin- 
ning conventionally occurs at a higher temperature than opera- 
tion of the LIX circuit, the strip solution is heated passing to 
electrowinning and cooled passing from electrowinning. Cop- 
per is then removed from the nickel-free organic by countercur- 
rent stripping with depleted electrolyte from copper electro- 
winning. The copper electrolyte is also heated-cooled on pas- 
sage to-from electrowinning to permit operation of electrowin- 
ning at a higher temperature. Makeup organic is added to the 
stripped reagent to offset degradation and soluble organic 
losses to the pregnant liquor, and the metal-free organic is 
recycled to extraction. 

COPPER ELECTROWINNING— 
COMMERCIAL (FIG. A-9) 

Cathode copper is recovered from the strong electrolyte 
from LIX using conventional technology. Starter sheets are 
deposited on titanium blanks from a strong electrolyte and are 
removed, washed, looped, and returned to the commerical 
section as starters. Full-term cathodes produced in the com- 
mercial section are washed, unloaded, and prepared for ship- 



13 



Table A-1.— Operating parameters for gas reduction and ammoniacal leach process 



Parameter and unit 



Parameter and unit 



ORE PROCESSING AND DRYING (FIG. A-2) 



LIQUID ION EXCHANGE-STRIPPING (FIG. A-8)— Con. 



Feed rate, wet basis (330 days/yr; 24 hr/day) tpd.. 

Feed size to reduction mesh.. 

Drying temperature ° C. 



REDUCTION (FIG. A-3) 



Reductant gas composition, pet: 

CO 

CO2 

H2 

Nz 

HjO 

CH4 
Gas temperature 
Reduction temperature 
Mn cartwnation 
Cooling temperature 
Reduction reactions 

MnOa + CO— > MnO + COz 

FejOs + CO — > 2FeO + CO2 

NiO + CO— > Ni + CO2 

CuO + CO— >Cu + CO2 

CoO + CO— > Co + CO2 
Conversion, pet: 

Co 

Cu 

Fe 

Mn 

Ni 



LEACHING-AERATION (FIG. A-4) 



Number of stages 

Temperature 

Time per stage 

Leach solution composition, gpl 

NH3 

CO2 
Pressure 
Solubilization of metals, pet 

Co 

Cu 

Fe 

Mn 

Mo 

Ni 

Zn 



SOLID-LIQUID SEPARATION (FIG A-5) 



Underflow density 

Wash ratio 

Wash recovery 

Wash liquor compMSsition, gpl 



pet solids 

kg/kg liquor 

pet 



CO, 



LIQUID ION EXCHANGE-EXTRACTION (FIG. A-6) 



Extraction: 

Extractant 

Number of stages 

Organic-aqueous ratio.. 
Metals extraction, pet: 
Co 



Cu 

Ni 

Zn 

Washing (primary): 

Washing agent pet NHa.. 

Number of stages 

Organic-aqueous ratio 

3 in organic gpl.. 



LIQUID ION EXCHANGE-STRIPPING (FIG. A-( 



Washing (secondary): 
Wash composition, gpl: 

(NH4)2S04 

H2SO4 



10,900 
-65 
150 



18.2 
7.8 

10.9 

49 

10.1 
3.6 

825 

625 
95 
125 



100 
100 



98 
100 



100 
50 

1 



35-40 
2 



100 
50 



'LIX64N 
3 

2:1 



99.9 
99.9 
10 



Washing (secondary) — Con. 

Number of stages 
Organic-aqueous ratio 
Residual NH3 in organic 
Ni stripping 
Stnp solution composition, gpl 

Cu 

HzSO* 

Ni 

Zn 
Number of stages 
Organic-aqueous ratio 
Stripping, pet 

Co 

Cu 

Ni 

Zn 

Cu stripping: 
Strip solution composition, gpl: 

Cu 

H2SO4 

Ni (max) 

Zn 
Number of stages 
Organic-aqueous ratio 
Stnpping, pet 

Co 

Cu 

Ni 

Zn 
Temperature 



gpl 



2 

1:1 
0.01 



< 0.001 
40 
50 
«0 

3 
5:1 

0.3 

<.004 
98.8 
«0 



40 
160 

10 
5 
2 

3:1 

0.2 
87 
«0 
100 
40 



COPPER ELECTROWINNING— COMMERCIAL (FIG. A-! 



Current density 
Current efficiency 
Temperature 
Cu in-out 
H2SO4 in-out 



A/m^. 
pet. 
°C. 
gpl 

gpl 



NICKEL ELECTROWINNING— COMMERCIAL (FIG 



Current density 
Current efficiency 
Temperature 
Ni in-out. 
H2SO4 in-out 
Na2S04.. 
H3BO3.... 



A/m^. 
pet, 

"C, 

gpl 
gpl 
gpl 



53-40 
160-180 



180 
93 
60 
75-50 
0.016-40 
100 
15 



COBALT RECOVERY (FIG A-11) 



Precipitating agent 

Precipitation, pet: 

Co 

Cu 

Ni 

Zn 
Temperature 
Clarifier density 
Wash ratio 
Co leaching slurry 
Leaching agent 

Evaporation-crystallization water removal 
Co oxidation 

Temperature 



.pet NH4HS.. 



Co reduction 
Temperature 
Pressure 
Reductant 



"C 
pet solids 

pet 

pet H2SO4 

pet 

°C 
psig 

°C 
psig 



40 
70 
70 

100 
150 

175 
500 
H, 



AMMONIA RECOVERY (FIG A-1 2) 



CO2 
Temperature 
Pressure 

Efficiency for CO2 
Number of stages 



°C 
atm 
pet 



^Reference to specific trade names does not imply endorsement by the Bureau of Mines. 



14 



Table A-1 . — Operating parameters for gas reduction and ammoniacal leach process — Continued 



Parameter and unit 


Value 


Parameter and unit 


Value 


AMMONIA RECOVERY (FIG. A-1 2)— Con. 


AMMONIA RECOVERY (FIG. A-1 2)— Con. 


NH3 absorber: 

Temperature °C.. 

Pressure atm.. 

Number of stages 


35 

1.2 

1 


NHg stripper: 

Pressure atm.. 

Recovery of NH3 pet.. 


1.5 
99 
2 









ment to sale. The greater portion of the wealt electrolyte is 
recycled to the LIX section for stripping. A small amount of 
nickel is stripped along with the copper not deposited in 
electrowinning, and must be purged from the system. The 
purged electrolyte passes through purification cells where 
copper is removed by electrowinning to depletion. The 
decopperized electrolyte passes to vacuum evaporators where 
water is removed and nickel sulfate is precipitated from the 
resulting highly acidic solution. The nickel sulfate is removed 
and sent to cobalt recovery where it is combined with other 
purge streams. The acid is retumed to the process where, with 
makeup acid, it is used to dissolve scrap copper for return to 
the commercial cells for deposition. Sufficient steam, wash 
water, and makeup water are added to the circuit to offset 
water vaporized or carried off with evolved oxygen during 
electrowinning. 



NICKEL ELECTROWINNING— 
COMMERICAL (FIG. A-10) 

Nickel is recovered from the strong electrolyte by electrowin- 
ning in a manner similar to that used for copper recovery. In 
nickel electrowinning, however, cathode bags are used, and 
sodium sulfate and boric acid are added to the electrolyte to 
control its conductivity and pH. Dissolved organic carried from 
the LIX step is removed by adsorption on activated carbon 
prior to any electrolyte passing to electrowinning. Also, the 
starter sheets are pickled in H2SO4 prior to use in the commer- 
cial cells, and nickel scrap is dissolved in ammonia-containing 
raffinate and recycled to the pregnant liquor, rather than to the 
recycled or makeup ackJ solutk>n. The electrolyte purge required 
to remove impurities from the electrowinning circuit passes to 
a sulfide precipitation reactor and then to cobalt recovery for 
recovery of metal values. 



COBALT RECOVERY 
(FIG. A-1 1) 

Along with unextracted Cu, Ni, and Zn, Co is recovered from 
the LIX raffinate by precipitation with ammonium hydrosulfide 
(produced by sparging hydrogen sulfide into an excess of 
ammonia solution). The sulfide precipitate is separated from 
the raffinate in a clarifier, with the clarifier overflow being 
recycled for tailings washing and the underflow passing to 
stripping for ammonia recovery. 

The sulfide slurry is mixed with electrolyte purges from Cu 
and Ni electrowinning, and with Co recovered from stripping 
the LIX reagent. The mixture is pressure leached with air to 
preferentially dissolve the Ni and Co sulfides, leaving the Cu 
and Zn sulfides in the residues. The latter are removed by 



filtration and sold as minor products to smelters for recovery of 
metal values. 

Following pH adjustment and reprecipitation with hydrogen 
sulfide for final removal of any Zn and Cu solubilized in the first 
leach, the Ni-Co sulfate solution is heated and autoclaved, 
and Ni is reduced with hydrogen. Sufficient ammonia solution 
is added during reduction to neutralize the acid formed. Only a 
portkxi of the nk^el is removed per pass to prevent oven-eductkxi 
and subsequent contamination of the nickel powder with cobalt. 
After densification through repeated recycle, the nickel pow- 
der is removed, washed, and passed to drying and briquetting 
for sale. 

The largely nickel-free cobalt sulfate solution passes to an 
evaporator-crystallizer where the remaining nickel and cobalt 
are precipitated as the double salts with ammonium sulfate. 
Excess ammonium sulfate is purged, and the salts are redis- 
solved in strong ammonia solution. The cobalt in solution is 
oxidized to the cobaltic state (Co^^) with air. This permits the 
cobalt to remain in solution when the stream is acidified to 
remove the nickel salts, which are separated and recycled to 
the pH adjustment step. The nickel-free solution is then heated 
and autoclaved for removal of cobalt by hydrogen reduction. 
Sufficient ammonia is added to neutralize the acid generated. 
The cobalt powder is dried and briquetted for sale, while the 
ammonium sulfate is purged to the ammonia recovery process. 



AMMONIA RECOVERY (FIG. A-1 2) 

Tailings from the CCD wash circuit are preheated and stripped 
for ammonia recovery by countercurrent contact with steam in 
stripping towers. The steam and ammonia vapors from strip- 
ping are combined with vapors from other ammonia strippers 
and pass to an ammonia absorber-condenser tower where 
nx)st of the ammonia and amnronium carbonate are condensed. 
Vent gases pass to a cart}on dioxide absorber where they are 
absorbed, along with the required makeup carbon dioxide 
obtained from boiler offgases, in makeup scrubbing water. 
Ammonia is recovered from all process vents by countercur- 
rent contact with makeup scrubbing water in an ammonia 
absorber and vent scrubber. The ammonia-free gases pass to 
stacks for disposal. 

Ammonia is recovered from the ammonium sulfate purges 
from cobalt recovery and the LIX washing step by reaction with 
slaked lime. Steam is blown into the mixture to strip the evolved 
ammonia, and the vapor is condensed. The condensate is 
retumed to aqueous ammonia storage for recycle within the 
process. The gypsum slurry from the lime boil is cooled, along 
with the slurry from the tailings stripping, and passed to tailings 
surge. This is combined with process solid and liquid wastes 
and plant runoff, treated for pH control, as required, and pumped 
to the tailings impoundment area for disposal. 



15 



PLANT SERVICES 



PROCESS ALTERNATIVES 



Plant services include process and cooling water supply 
and treatment, steam raising and power generation, gas 
treatment, and reducing gas preparation. Makeup water is 
clarified and softened for distribution to the process, as required. 
Additional treatment is required for cooling tower water makeup, 
boiler feed water makeup, and for supplying plant potable 
water. Offgases from manganese reduction are burned, along 
with additional coal, in the main boilers to raise the required 
process steam and generate a portion of the power required in 
the process. Following particulate removal, the flue gases are 
combined with other process offgases and pass to gas treatment, 
where sulfur oxides and other acidic constituents are removed 
by scrubbing with limestone. The scrubbed offgases are 
reheated, combined with scrubbed vents from ammonia 
recovery, and are passed to stacks for disposal. Gas for 
nodule reduction is produced in a two-stage entrained-flow 
gasifier in which coal is mixed with preheated air and high- 
temperature steam for the production of a cartx)n monoxide- 
rich reducing gas. The gasifier product passes to reduction 
following particulate removal and energy recovery, with sulfur 
removal taking place after combustion and with other boiler 
flue gases. 



MANGANESE 
PRODUCTION ADD-ON 

The recovery of manganese from ammoniacal leach tails is 
an option that has been investigated. Manganese may be 
partially recovered from tailings by flotation of the fine MnCOa 
present. The MnCOa could then be converted to an oxide form 
for feed to produce ferromanganese or other manganese 
alloys. The recovery of manganese from the process tails 
would be contingent on the market conditions and process 
economics. Some intermediary product may have market value, 
thereby avoiding energy-intensive steps to produce manga- 
nese alloys. Because of the relatively new technology required 
for manganese recovery from ammoniacal leach tails, and the 
dependency upon economics and technical conditions, no 
detailed flowsheets are presented for this process. 



A major processing alternative, involving the hydrometallur- 
gical reduction-ammoniacal leaching of nodules is fully docu- 
mented in appendix B. 

Other than the metals separation and purification steps, the 
process configuration is based on the well-known Caron process, 
and there is little reason to believe, in the absence of actual 
operating data, that the fundamental approach should differ. 

It has been assumed that the reduced nodules can be 
carbonated in a fluid bed cooler prior to leaching. If carbona- 
tion is not complete, the nodules would absorb carbon dioxide 
directly from the leach liquor. Then, to maintain the required 
pH, the wash liquor would have to be recycled with a higher 
ammonium carbonate content. This, in turn, would be obtained 
by scrubbing a much larger fraction of the boiler flue gases in 
the ammonia recovery section. 

The use of fluid bed dryers and reactors represents an 
advance in processing technology over the use of rotary kilns 
and multiple hearth furnaces and should not drastically affect 
any material balance. It has been assumed that the leached 
tails can be stripped for ammonia recovery in the same way as 
is done in laterite processing, although unexpected fouling 
tendencies could require the use of less efficient stripping 
devices, thereby increasing steam (fuel) consumption. 

The ammonium sulfate solutions purged from the liquid ion 
exchange-extraction and cobalt recovery sections have been 
treated with lime for the recovery of ammonia for recycle. An 
alternative approach would involve direct recovery of ammo- 
nium sulfate by evaporation-crystallization, for sale as a 
byproduct. 

Alternative configurations of the metals separation steps 
are possible, such as selective extraction-selective stripping, 
but their impact on overall plant material and energy balances 
should be minor. Many variations are possible in the details of 
the scheme used for recovery of cobalt from a mixed sulfide 
precipitate. Ultimately, however, their impact on plant require- 
ments would not differ greatly from the approach used here, 
because the sulfides will still be oxidized to sulfates, purged, 
and hydrogen reduced. It does not appear likely that solutions 
could be purified easily enough to permit recovery of electro- 
lytic cobalt. 



16 



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o 



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11 
o 8 



Pv 


o 






n, 








rN>_ 


O 








\> 



17 




J? 



19 




?? 



20 




21 




22 



"QD 



! 
II 




23 




'^-^5:^ 



24 




25 




27 






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n 







APPENDIX B.— CUPRION AMMONIACAL LEACH PROCESS 



The Cuprion ammoniacal leach process is a three-metal 
process in which Cu, Ni, and Co are liberated in an ammoniacal- 
ammonium carbonate leach following a reduction-leach step. 
Carbon monoxide is used to regenerate the cuprous ion which 
reduces manganese dioxide. Copper and nickel are co-extracted 
by liquid ion exchange (LIX) reagents and are selectively 
stripped and recovered as electrowon cathodes. Cobalt is 
removed from the raffinate by precipitation with hydrogen 
sulfide and is recovered from the sulfide precipitate, along with 
some Ni, Zn, and Cu, by selective leaching and hydrogen 
reduction. The metal-free raffinate is steam stripped to recover a 
high-strength ammonia solution for recycle to the tailings wash 
step, together with ammonia and ammonium carbonate recov- 
ered by steam stripping the leach tailings. 

Detailed descriptions of each segment of the process are 
given for the following flowsheets. A summary of parameters 
for each section is given in table B-1 . A key to the flowsheet 
symbols is given in figure B-1 . 



ORE PREPARATION 
(FIG. B-2) 

Wet nodules are reclaimed from storage and fed through a 
primary cage mill where they are reduced to minus % in. They 
then pass to a rod mill for wet grinding to minus 65 mesh. 
Oversized nodules are separated and returned via the rake 
classifier, hydrocyclone, water-recycle circuit. The ground nod- 
ule slurry passing through the cyclone is held in an air-agitated 
surge tank to prevent settling before being pumped to the 
reduction step. 



REDUCTION-LEACH 
(FIG. B-3) 

The nodule slurry is mixed with recycled strong ammonia 
solution and fed, with a recycled solution containing an excess 
of cuprous ion (Cu*), to a train of agitated reduction reactors. 
The dilute slurry is contacted with a carbon monoxide-rich gas 
derived from gasified coal, the manganese dioxide is reduced 
and converted to manganese carbonate, and most of the 
value metals are solubilized. The heat of reaction is removed 
in shell and tube exchangers to maintain the reduction temper- 
ature at 50° C, and excess gases pass to ammonia recovery. 
The reduced, dilute nodule slurry is thickened with the over- 
flow recycle, and the thickened pulp passes to the oxidation 
leach. 



OXIDATION-LEACH 
(FIG. B-4) 

The reduced nodule slurry passes to a countercurrent oxidiz- 
ing leach in which air is sparged into the leach slurry to oxidize 
residual Cu * to Cu^ \ Co^ * to Co^ ' , and Fe^ * to Fe^ * , precipi- 
tating the Fe as an insoluble ferric hydroxide in the manga- 
nese carbonate tailings. Liquid-solid separations are made in 
thickeners, which also provide residence time for leaching. 
Offgases from aeration pass to ammonia recovery, leached 
nodules to washing, and pregnant liquor to LIX for metal 
separation and purification. 



SOLID-LIQUID 
SEPARATION (FIG. B-5) 

Metal values that have been solubilized in leaching and 
absorbed on tailings are recovered from the tailings by wash- 
ing in a countercurrent decantation (CCD) circuit using cov- 
ered thickeners. Wash liquor consists of recovered ammonia 
and ammonium carbonate along with raffinate from cobalt 
recovery. Washed tailings pass to stripping for ammonia and 
ammonium carbonate recovery while the wash overflow passes 
to leaching. 



LIQUID ION EXCHANGE- 
EXTRACTION (FIG. B-6) 

Pregnant liquor from leaching is filtered and passes to a 
three-stage, countercurrent LIX extraction circuit where copper, 
nickel, and some ammonia are removed from the pregnant 
liquor. Most of the ammonia is removed from the organic 
phase by washing with a weak aqueous ammonia solution. 
This ammonia is recovered by steam stripping a portion of the 
scrub solution, with the vapors passing to the ammonia recov- 
ery section. Provision is made for periodically cleaning the 
mixer-settler units used in extraction and stripping and for 
recovering organic and aqueous phases for recycle. Degraded 
organic, dust, and other forms of "crud" are removed from the 
organic and incinerated. Because a small amount of Co is 
co-extracted and is not stripped with Cu and Ni, it must be 
removed from the LIX reagent to prevent its buildup. This is 
accomplished by precipitating the cobalt, with hydrogen sulfide, 
from a purge stream of organic. The precipitated solids are 
washed from the organic and pass to cobalt recovery, while 
the purified organic is returned to the extraction loop (fig. B-7). 



LIQUID ION EXCHANGE- 
STRIPPING (FIG. B-8) 

The remainder of the ammonia is removed from the loaded 
organic by washing with a slightly acidic ammonium sulfate 
solution. The ammonium sulfate formed in scrubbing is purged 
to ammonia recovery. Nickel is then selectively stripped from 
the organic by countercurrent contact at controlled pH with 
depleted electrolyte from nickel electrowinning. Because elec- 
trowinning conventionally occurs at a higher temperature than 
operation of the LIX circuit, the strip solution is heated passing 
to electrowinning and cooled passing from electrowinning. 
Copper is then removed from the nickel-free organic by coun- 
tercurrent stripping with depleted electrolyte from copper 
electrowinning. The copper electrolyte is also heated-cooled 
on passage to-from electrowinning to permit operation of elec- 
trowinning at a higher temperature. Makeup organic is added 
to the stripped reagent to offset degradation and soluble organic 
losses to the pregnant liquor, and the metal-free organic is 
recycled to extraction. 



COPPER ELECTROWINNING— 
COMMERCIAL (FIG. B-9) 

Cathode copper is recovered from the LIX strong electrolyte 
using conventional technology. Starter sheets are deposited 



29 



Table B-1.— Operating parameters for Cuprion ammoniacal leach process 



Parameter and unit Value 


Parameter and unit Value 


ORE PREPARATION (FIG. B-2) 


LIQUID ION EXCHANGE-STRIPPING (FIG. B-8) 










Feed size to reduction ....mesh.. —65 


WdsnjnQ (SGConoflry)' 










REDUCTION-LEACH (FIG. B-3) 


H2S04. 1 


Reductant gas composition, pet 
CO 40-60 
Ha 3^45 
H2O 6-12 
N2 1 
Temperature ° C 50 
Pressure atm. 1 

Mn02 + CO— >MnC03 
FejOa + CO-> 2FeO + COj 
NiO + CO->Ni + C02 
CuO + CO— >Cu + CO2 
CoO + CO->Co + C02 

NH3 100 


Organic-aqueous ratio 1 :1 
Residual NH3 in organic gpl 0.01 
Ni stripping: 
Strip solution composition, gpl 

Cu <0.001 

H2S04. 40. 

Ni 50 

Zn so 

Number of stages 3 
Organic-aqueous ratio 5:1 
Stripping, pet 
Co 0.3 
Cu <.004 
Ni 98.8 
Zn *0 


CO2 25 
Cu 3-5 

Number of stages 6 

Reduction, pet 
Co 50 
Cu 80 
Mn 97 
Mo 80 
Ni 90 
Zn 40 

Slurry density pet solids 20-30 


Cu stnpping 

Stnp solution composition, gpl: 

Cu 40 

H2SO4 160 
Ni (max) 10 
Zn 5 

Number of stages 2 

Organic-aqueous ratio 3:1 

Stnpping, pet 
Co 0.2 
Cu 87 


OXIDATION-LEACH (FIG. B-4) 


Ni so 


Pregnant liquor composition, gpl: 
NHa 100 


Zn 100 
Temperature ° C 40 


COi 25 


COPPER ELECTROWINNING— COMMERCIAL (FIG B-9) 


Cu 4-8 

Ni 5-10 

Temperature " C 50 

Pressure atm 1 

Recovery, pet 

Co 50 


Current density A/m^ 180 
Cun-ent efficiency pet 94 
Temperature ° C 50 
Cu in-out gpl 53-40 
H2S04in-out gpl 160-180 


Cu 90 


NICKEL ELECTROWINNING-COMMERCIAL (FIG B-10) 


Ni 90 


Cun-ent density A/m^ 180 
Current effiaency pet 93 


SOLID-LIQUID SEPARATION (FIG B-5) 


Wash ratio kg/kg liquor 2 
Wash recovery pet 98 
Number of stages 6 
Wash liquor composition, gpl 
NHa 100 


Temperature ° C 60 
Ni in-out gpl 75-50 
H2S04in-out gpl 0.016-40 
Na2S04 gpl 100 
HaBOa gpl 15 


COBALT RECOVERY (FIG. B-1 1 ) 


CO2 50 


Precipitating agent pet NH4HS 30 


LIQUID ION EXCHANGE-EXTRACTION (FIG B-6) 


Predpitation. pet: 


Exti action 
Extractant 'LIX 64N 
Number of stages 3 
Organic-aqueous ratio 2:1 
Metals extraction, pet 
Co 1 
Cu 99.9 
Ni 99.9 
Zn 10 
Washing (primary) 
Washing agent pet NH, 1 
Number of stages 2 
Organic-aqueous ratw 3:1 
Residual NH, in organic gpl 0.1 


Co 98 

Cu 99.9 

Ni 99 

Zn 99.9 

Temperature ° C 80 

Clanfier density pet solids 5 

Wash ratio 2:1 

Co leaching sluny pet 40 

Leaching agent pet H2SO4 70 

Evaporation-crystallization water removal pet 70 

Co oxidation 

Temperature "C 100 

Pressure psig 150 

Co reduction 

Temperature °C 175 

Pressure psig 500 

Reductant Hj 



'Reference to specific tradenames does not impty endorsement by the Bureau of Mines. 



30 



Table B-1 .—Operating parameters for Cuprion ammoniacai leach process— Continued 





Parameter and unit 




Value 




Parameter and unit 




Value 


AMMONIA RECOVERY (FIG. B-1 2) 


AMMONIA RECOVERY (FIG. B-1 2)— Con. 


CO2 absorber: 

Temperature 

Pressure 

EfficierKy for CO2 

Number of stages 
NH3 absorber: 

Temperature 




..°C.. 
atm.. 
..pet.. 


40 
1.2 
99 

1 

35 


NH3 absorber— Con. 

Pressure 

Number of stages. 
NH3 stripper: 

Pressure 

Recovery of NH3.. 

Number of stages. 




atm.. 

atm.. 

pet.. 


1.2 

1 

1 5 




..°C.. 


99 
2 



on titanium blanks from strong electrolyte and are removed, 
washed, looped, and returned to the commercial section as 
starters. Full-term cathodes produced in the commercial sec- 
tion are washed, unloaded, and prepared for shipment to sale. 
The greater portion of the weak electrolyte is recycled to the 
LIX section for stripping. A small amount of nickel is stripped 
along with the copper not deposited in electrowinning, and 
must be purged from the system. The purged electrolyte passes 
through purification cells where copper is removed by electro- 
winning to depletion. The decopperized electrolyte passes to 
vacuum evaporators where water is removed and nickel sul- 
fate is precipitated from the resulting highly acidic solution. 
The nickel sulfate is removed and sent to cobalt recovery 
where it is combined with other purge streams. The acid is 
returned to the process where, with makeup acid, it is used to 
redissolve scrap copper for return to the commercial cells for 
deposition. Provisions are made for recycling copper, in ammo- 
nium carbonate solution, to reduction if required. Sufficient 
steam, wash water, and makeup water are added to the circuit 
to offset water vaporized or carried off with evolved oxygen 
during electrowinning. 



NICKEL ELECTROWINNING— 
COMMERCIAL (FIG. B-10) 

Nickel is recovered from the strong electrolyte by electrowin- 
ning in a manner similar to that used for copper recovery. In 
nickel electrowinning, however, cathode bags are used, and 
sodium sulfate and boric acid are added to the electrolyte to 
control its conductivity and pH. Dissolved organic carried from 
the LIX step is removed by adsorption on activitated carbon 
before the nickel electrolyte passes to electrowinning. Also, 
the starter sheets are pickled in H2SO4 prior to use in the 
commercial cells, and nickel scrap is redissolved in ammonia- 
containing raffinate and recycled to the pregnant liquor, rather 
than to the recycled or makeup acid solution. The electrolyte 
purge required to remove impurities from the electrowinning 
circuit passes to a sulfide precipitation reactor and then to 
cobalt recovery for recovery of metal values. 



COBALT RECOVERY (FIG. B-11) 

Along with unextracted Cu, Ni, and Zn, Co is recovered from 
the LIX raffinate by precipitation with a slight excess of ammo- 
nium hydrosulfide (produced by sparging hydrogen sulfide 
into an excess of ammonia solution). The sulfide precipitate is 
separated from the raffinate in a clarifier, with the clarifier 
overflow being recycled to ammonia recovery and the under- 
flow passing to stripping for ammonia recovery. 



The sulfide slurry is mixed with electrolyte purges from Cu 
and Ni electrowinning, and with the Co recovered from strip- 
ping the LIX reagent. The mixture is pressure-leached with air 
to preferentially dissolve the Ni and Co sulfides, leaving the Cu 
and Zn sulfides in the residues. The latter are removed by 
filtration and sold as minor products to smelters for recovery of 
metal values. 

Following pH adjustment and reprecipitation with hydrogen 
sulfide for final removal of any Zn and Cu solubilized in the first 
leach, the Ni-Co sulfate solution is heated and autoclaved, 
and Ni is reduced with hydrogen. Sufficient ammonia solution 
is added during reduction to neutralize the acid formed. Only a 
portion of the nickel is removed per pass to prevent overreduction 
and subsequent contamination of the nickel powder with cobalt. 
After densification through repeated recycle, the nickel pow- 
der is removed, washed, and passed to drying and briquetting 
for sale. 

The largely nickel-free cobalt sulfate solution passes to an 
evaporator-crystallizer where the remaining nickel and cobalt 
are precipitated as the double salts with ammonium sulfate. 
Excess ammonium sulfate is purged, and the salts are redis- 
solved in strong ammonia solution. The cobalt in solution is 
oxidized to the cobaltic state (Co^^) with air. This permits 
the cobalt to remain in solution when the stream is acidified to 
remove the nickel salts, which are separated and recycled to 
the pH adjustment step. The nickel-free solution is then heated 
and autoclaved for removal of cobalt by hydrogen reduction. 
Sufficient ammonia is added to neutralize the acid generated. 
The cobalt powder is dried and briquetted for sale, while the 
ammonium sulfate is purged to the ammonia recovery process. 



AMMONIA RECOVERY (FIG. B-1 2) 

Tailings from the CCD wash circuit are preheated and stripped 
for ammonia and carbon dioxide recovery by countercurrent 
contact with steam in stripping towers. The steam and ammonia- 
carbon dioxide vapors from tailings stripping are combined 
with vapors from cobalt sulfide slurry stripping, condensed, 
and combined with ammonia and carbon dioxide scrubbed 
from process vent streams. Makeup carbon dioxide is obtained 
from boiler offgases by countercurrent contact with scrubbing 
water; the ammonia-free gases pass to stacks for disposal. 
The ammonia-rich ammonium carbonate solution required in 
reduction is obtained by stripping only a portion of the ammo- 
nia contained in the raffinate stream from cobalt recovery. 
These ammonia-rich vapors are combined with ammonium- 
steam vapors from the LIX ammonia recovery and lime boil 
steps, makeup ammonia, and ammonia-rich vapors from reduc- 
tion and oxidation vents, and are condensed and recycled to 
reduction. The raffinate is then stripped further, with the ammo- 



nium carbonate recycled to tailings washing and the stripper 
bottoms used for process water makeup. 

Ammonia is recovered from the ammonium sulfate purges 
from cobalt recovery and the LIX washing step by reaction with 
slaked lime. Steam is blown into the mixture to strip the evolved 
ammonia, and the vapor is condensed, with the condensate 
returned for recycle within the process. The gypsum slurry 
from the lime boil is cooled, along with the slurry from the 
tailings stripping, and passed to tailings surge. This is com- 
bined with the process solid and liquid wastes and plant runoff, 
treated for pH control as required, and pumped to the tailings 
impoundment area for disposal. 



PLANT SERVICES 

Plant services include process and cooling water supply 
and treatment, steam raising and power generation, gas 
treatment, and reducing gas preparation. Makeup water is 
clarified and softened for distribution to the process as required. 
Additional treatment is required for cooling tower water makeup, 
boiler feed water makeup, and for supplying plant potable 
water. The carbon monoxide required for manganese reduc- 
tion is produced in a low-pressure gasifier in which coal is 
mixed with oxygen and steam and partially combusted. Acid 
gases are removed from the reducing gas, following particu- 
late removal, and are sent to the main boilers to oxidize 
reduced components for subsequent recovery. High-strength 
carbon monoxide is then removed from the sweetened gases 
for use in reduction, and the remaining gases, mainly hydrogen, 
are sent to the main boilers except for the amount required in 
cobalt reduction. 

These and other combustible process offgases are burned, 
along with additional coal, in the main boilers to raise the 
required process steam and to generate a portion of the power 
required in the process. Following particulate removal, the flue 
gases are combined with other process offgases and pass to 
gas treatment, where sulfur oxides and other constituents are 
removed by scrubbing with limestone. The scrubbed offgases 
are reheated, combined with scrubbed vents from ammonia 
recovery, and are passed to stacks for disposal. 



MANGANESE PRODUCTION ADD-ON 

The recovery of manganese from ammoniacal leach tails is 
an option that has been investigated. Manganese may be 
partially recovered from tailings by flotation of the fine MnCOa 
present. The MnCOa could then be converted to an oxide form 
for feed to produce ferromanganese or other manganese 
alloys. The recovery of manganese from the process tails 
would be contingent on the market conditions and process 



economics. Some intermediary product may have market value, 
thereby avoiding energy-intensive steps to produce manga- 
nese alloys. Because of the relatively new technology required 
for manganese recovery from ammoniacal leach tails, and the 
dependency upon economic and technical conditions, no detailed 
flowsheets are presented for this process. 



PROCESS ALTERNATIVES 

A major process alternative, involving the pyrometallurgical 
reduction-ammoniacal leaching of nodules, is fully documented 
in appendix A. 

While the pyrometallurgical reduction-ammoniacal leaching 
process is closely based on the well-known Caron process, 
the Cuprion process differs in two important respects: the 
metals separation scheme is specific to nodules processing 
and the dififering ammonium carbonate concentrations required 
in reduction and tailings washing complicate the ammonia 
recovery step. 

Alternative configurations of the metals separation steps 
are possible, such as selective extraction-selective stripping, 
but their impact on overall plant material and energy balances 
should be minor. Many variations are possible in the details of 
the scheme used for recovery of cobalt from a mixed sulfide 
precipitate. Ultimately, however, their impact on plant require- 
ments would not differ greatly from the approach used here, 
because the sulfides will still be oxidized to sulfates, purged, 
and hydrogen reduced. It does not appear likely that solutions 
could be purified easily enough to permit recovery of electro- 
lytic cobalt. 

Tailings stripping for ammonia and carbon dioxide recovery 
has been based on the Caron practice, but the raffinate strip- 
ping operation is unique to this process. No operating data are 
available to support the energy-intensive concept used. It is 
possible that other techniques, such as vacuum or pressure 
stripping, pH adjustment prior to stripping, extractive distillation, 
etc., may be more advantageous if other process constraints, 
such as the overall water balance, can also be met. 

The ammonium sulfate solutions purged from the liquid ion 
exchange-extraction and cobalt recovery sections have been 
treated with lime for the recovery of ammonia for recycle. An 
alternative approach would involve direct recovery of ammo- 
nium sulfate by evaporation-crystallization, for sale as a 
byproduct. 

It has been assumed that, except for the cobalt reduction 
requirements, byproduct hydrogen from carbon monoxide pro- 
duction would be burned for its fuel value, which is a relatively 
poor use. A small part (1 pet) of the hydrogen could be burned 
with 4,000-tpy sulfur to produce the required amount of hydro- 
gen sulfide. 



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44 



APPENDIX C— HIGH-TEMPERATURE AND HIGH-PRESSURE H2SO4 LEACH PROCESS 



The high-temperature and high-pressure H2SO4 leach proc- 
ess is a three-metal process in which Cu, Ni, and Co are 
selectively leached from the nodules by strong H2SO4 at high 
temperature and high pressure. After separation of the leach- 
ing residue and metalliferous solution by washing, the copper 
and nicl<el are co-extracted by liquid ion exchange (LIX) reagents 
and are selectively stripped and recovered as electrowon 
cathodes. Cobalt is separated from the raffinate by precipita- 
tion with hydrogen sulfide and is recovered from the sulfide 
precipitate, along with some Ni, Cu, and Zn, by selective 
leaching and hydrogen reduction. The metal-free raffinate is 
recycled to the washing process. Ammonia consumed in the 
process is recovered and recycled to the process for use in pH 
control. 

Detailed descriptions of each segment of the process are 
given for the following flowsheets. A summary of operating 
parameters for each section is given in table C-1 . A key to the 
iflowsheet symbols is given in figure C-1 . 



ORE PROCESSING (FIG. C-2) 

Wet nodules are reclaimed from storage and fed through a 
primary cage mill where they are reduced to minus % in. They 
then pass to a rod mill for a second and final size reduction to 
minus 65 mesh. Oversized nodules that escape the initial rod 
milling are separated and returned via a rake classifier, 
hydrocyclone, water-recycle circuit. The ground nodule slurry 
passing through the hydrocyclone is held in an air-agitated 
surge tank to prevent settling until it can be fed to the high- 
temperature H2SO4 leach reactors. 



LEACHING (FIG. C-3) 

Slurried nodules enter a steam-sparged preheater along 
with the pregnant liquor of recycled leach solution containing 
the metal values. The solution at 105° C passes through a 
second steam-operated heat exchange step, reaching 1 70° C 
by use of sparged steam. A final temperature of 245° C is 
reached within the leach reactors, where contact with H2SO4 is 
made. After a set residence time within the reactors, the slurry 
passes through two pressure and one vacuum flash stage for 
steam heat recovery and slurry temperature reduction to 50° 
C. 



SOLID-LIQUID SEPARATION (FIG. C-4) 

Metal values that have been solubilized in acid leaching are 
recovered from the tailings by washing in a countercurrent 
decantation (CCD) circuit using covered thickeners. Adequate 
residence time in this circuit allows recycled water to wash the 
solubilized metal values from the precipitated and unreacted 
solids that pass from the system to a waste disposal area. The 
pregnant liquor proceeds to an initial pH adjusting step in 
preparation for selective metal removal. 



PREGNANT LIQUOR pH ADJUSTMENT (FIG. C-5) 

The pH adjustment process removes the necessary resid- 
ual acid concentration of the pregnant liquor through the use of 



calcium carbonate (limestone). The calcium sulfate precipi- 
tate is sent to the wash circuit, while the neutralized pregnant 
liquor overflow of the clarifier goes to the copper LIX circuit. 



COPPER LIQUID ION EXCHANGE (FIG. C-6) 

The filtered pregnant liquor passes to a three-stage counter- 
current LIX circuit with interstage pH adjustment. Nearly com- 
plete removal of the Cu from the aqueous to the organic 
exchange liquid is accomplished along with the removal of 
small amounts of Ni, Co, and Zn. The loaded organic stream is 
countercurrently stripped of its copper value with depleted 
electrolyte from copper electrowinning. The copper electrolyte 
is heated on passage to electrowinning and cooled on pas- 
sage from electrowinning to permit operation of electrowin- 
ning at a higher temperature. Makeup organic is added to the 
electrolyte-stripped reagent to offset degradation and soluble 
organic losses to pregnant liquor. A continuous purge is oper- 
ated to prevent a buildup of impurities (fig. C-7). The aqueous 
raffinate stream containing the nickel, cobalt, and other metal 
values is sent to a neutralizing step prior to nickel recovery. 



COPPER ELECTROWINNING— 
COMMERCIAL (FIG. C-8) 

Cathode copper is recovered from the LIX strong electrolyte 
using conventional technology. Starter sheets are deposited 
on titanium blanks and are removed, washed, looped, and 
returned to the commercial section. Cathodes produced in the 
commercial section are washed, unloaded, and prepared for 
shipment to sale. The major portion of the weak electrolyte is 
recycled to the LIX section for stripping. A small purge stream 
is recycled to the pH adjustment process to prevent a buildup 
of undesirable co-stripped metals other than copper. Makeup 
acid, used to redissolve scrap copper for return to the commer- 
cial cells for deposition, replenishes the weak electrolyte (a 
strong acid solution) for return to copper stripping. Sufficient 
steam, wash water, and makeup water are added to the circuit 
to offset water vaporized or carried off with evolved oxygen 
duhng electrowinning. 



COPPER RAFFINATE pH ADJUSTMENT (FIG. C-9) 

The nickel-bearing raffinate from copper LIX contains an 
excess of acid, which is neutralized with ammonia and made 
slightly basic before the nickel value can be removed. In 
addition to neutralization, tank aeration causes precipitation of 
Fe, Mn, Mg, and Al initially extracted from the nodules and 
carried with the raffinate. The precipitated metals are settled, 
centrifuged, and returned to the wash circuit before leaving the 
process as waste. The overflow raffinate containing some 
entrained precipitate overflows the settler and passes on to 
nickel LIX. 



NICKEL LIQUID ION EXCHANGE- 
EXTRACTION (FIG. C-1 0) 

The neutralized raffinate is filtered from the entrained 
precipitate, and then depleted of nickel by organic ion exchange 



45 



Table C-1 .—Operating parameters for high-temperature and high-pressure H2SO4 leach process 



Parameter and unit 


Value 


Parameter and unit 




Value 


ORE PROCESSING (FIG. C-2) 


NICKEL LIQUID ION EXCHANGE-EXTRACTION (FIG. C-10) 


Feed rate, wet basis (330 days/yr; 24 hr/day) tpd.. 


10,900 


Extraction: 






Feed size to leaching mesh.. 


-65 


Extractant 




LIX64N 


Pulp density, solids pet.. 


35-40 


Number of stages 




3 


LEACHING (FIG. C-3) 


Organic-aqueous ratio 
Temperature 


°C 


5:1 
40 


Temperature °C.. 


245 


Metals extraction, pet 






Pressure atm 


35 


Co 




1 


Acid feed pet H2SO4 


93 


Cu 




1 


Recovery, pet 




Ni 




99.5 


Co 


90 


Washing (primary) 






Cu 


95 


Washing agent 


pctNHa 


1 


Fe 


1 


Number of stages 




3 


Mn 


5 


Organic-aqueous ratio 




3.3:1 


Ni 


95 

90 

4 

0.4 


Residual NH3 in organic 


gpl 


0.1 


Zn 
Contact time hr 


NICKEL LIQUID ION EXCHANGE-STRIPPING (FIG. C-11) 


H2SO4 consumption lb/lb nodules 


Ammonia scrub (secondary) 






Leaching reactions 




Wash composition, gpl 






NiO + H2SO4 — > N1SO4 + H2O 




(NH4)2S04 




200 


CuO + H2SO4 — > CUSO4 + H2O 




H2SO4. 




1 


CoO + H2SO4 — > C0SO4 + H2O 




Number of stages 




2 


Mn02 + H2SO4— > Mn SO4 +H2O + 0.5 O2 




Organic-aqueous ratio 




1:1 


FezOa + 3H2SO4— > Fe2(S04)3 +3H2O 




Residual NH3 in organic 


gpl 


0.01 


SOLID-LIQUID SEPARATION (FIG. C-4) | 


Temperature 
Nickel stripping 


°C 


40 




6 


Strip solution composition, gpl: 
Cu 






Efficiency pet.. 


98 




< 0.001 


Underflow density pet solids 


35-40 


H2S04 




40 


Wash ratio kg/kg liquor.. 


2 


Ni 




50 


PREGNANT LIQUOR pH ADJUSTtWiENT (FIG. C-5) j 


Number of stages 
Organic-aqueous ratio 




3 
5:1 


Adjustment agent 


CaCOs 


Stnpping, pet 
Co 






H2SO4 concentration, final gpl.. 


0.5 




0.3 


Entrained solids ppm.. 


=100 


Cu 
Ni 




<.0O4 


COPPER LIQUID ION EXCHANGE (FIG. C-6) | 


98.8 


Extraction: 


LIX64N 


NICKEL ELECTROWINNING— COMMERCIAL (FIG C-12) 


Extractant 


Current density 


A/m^ 


180 


Number of stages 


3 


Current efficiency 


pet 


93 


Organic-aqueous ratio 


1:1 


Temperature 


°C 


60 


Metals extraction, pet 




Ni in-out 


gpl 


75-50 


Co 


0.1 


H2SO4 in-out 


gpl 


0.016-40 


Cu 


99.5 


Na2S04 


gpl 


100 


Fe 


.1 
.1 
.1 
1 


H3BO3 


gpl 


15 


Ni 


COBALT RECOVERY (FIG 


.c-1 3) 




Zn 


Precipitating agent 


pet NH4HS.. 


30 


Ammonia wash pet NH3 


25 


Precipitation, pet: 




Residual NH3 in organic gpl 


1 


Co 




98 


Stripping 




Cu 




99.9 


Strip solution concentration, gpl: 




Ni 




99 


H2SO4 


160 


Zn 




99.9 


Ni (max) 


10 


Temperature 


"C 


80 


Cu 


40 


Clanfier density 


pet solids 


5 


Zn 


5 


Wash ratio 




2:1 


Number of stages 


2 


Co leaching slurry 


pet 


40 


Organic-aqueous ratio 


3:1 


Leaching agent 


pet H2SO4 


70 


Temperature ° C 


40 


Evaporation-crystallization water removal 


pet 


70 


Stripping, pet 




Co oxidation 






Co 


0.2 


Temperature 


"C 


100 


Cu 


87 


Pressure 


psig 


150 


Ni 


.9 


Co reduction 






Zn 


100 


Temperature 

Pressure 

Reductant 


psig 


175 


COPPER ELECTROWINNING— COMMERCIAL (FIG C-8) 


500 


Current density A/m^ 
Current efficiency pet 


180 
94 
50 




AMMONIA RECOVERY (FIG. C-1 4) 


Temperature ° C 


NH3 absorber: 






Cu in-out gpl 


53-40 


Temperature 


"C. 


35 


H2S04 in-out gpl 


160-180 


Pressure 

Number of stages 

NH3 stripper: 
Pressure 


atm.. 


1.2 


COPPER RAFFINATE pH ADJUSTMENT (FIG. C-9) 


1 


Number of stages 


4 


atm.. 


1.5 






Recovery of NH3 

Number of stages 


pet.. 




Final pH 


=4.0 


2 







'Reference to specifictrade names does not imply endorsementby the Bureau of Mines. 



46 



extraction in three stages of pH-controlled countercurrent 
extraction. The nickel-depleted aqueous phase, containing 
primarily cobalt, proceeds to cobalt recovery The entrained 
aqueous, containing dissolved ammonia, extracted nickel, and 
trace metals, is removed from the organic phase in a liquid 
separation step. The ammonia removal requires two stages 
of recovery. The organic is countercurrently washed in two 
stages, and then the aqueous wash phase is steam stripped of 
ammonia. 



NICKEL LIQUID ION EXCHANGE- 
STRIPPING (FIG. C-11) 

The partially ammonia-stripped organic passes to a second 
step for reaction with H2SO4 to draw the remaining ammonia 
into an aqueous phase. The phases are countercurrently con- 
tacted and separated in two stages. The aqueous phase returns 
to nickel extraction. The organic phase, containing nickel and 
trace metal impurities, enters two countercurrent stages of 
nickel stripping with weak electrolyte from electrowinning. This 
electrolyte is heated passing to and cooled passing from nickel 
electrowinning which is operated at higher temperatures. Losses 
of the organic extractant during the stripping of nickel are 
replenished with fresh organic. A small amount of organic is 
purged to a trace metals removal step to prevent a buildup. 
The "cleaned" organic purge and makeup organic are com- 
bined with the nickel-free organic for recycle to the nickel LIX 
extraction step. 



NICKEL ELECTROWINNING— 
COMMERCIAL (FIG. C-1 2) 

Nickel is recovered from the strong electrolyte by electrowin- 
ning in a manner similar to that used for copper recovery. In 
nickel electrowinning, however, cathode bags are used, and 
the strong electrolyte is chemically conditioned with sodium 
sulfate and boric acid to control its conductivity and pH. Dis- 
solved organic, carried from the LIX step, is adsorbed on 
activited cartx)n prior to any electrolyte passing to electrowinning. 
Nickel is recovered in a manner similar to that used for copper 
recovery. The starter sheets are pickled in H2SO4 prior to use 
in the commercial cells, and nickel scrap is dissolved in ammonia- 
containing raffinate and recycled to the ion exchange process. 
The electrolyte purge required to remove impurities from the 
electrowinning circuit passes to raffinate neutralization. The 
strongly acidic, weak electrolyte returns to the nickel stripping 
circuit. 



COBALT RECOVERY (FIG. C-1 3) 

Along with any unextracted Cu, Ni, and Zn, Co is recovered 
from the Ni LIX raffinate by precipitation with ammonium hydro- 
sulfide (produced by sparging hydrogen sulfide into an excess 
of ammonia solution). The sulfide precipitate is separated 
from the raffinate in a clarifier. The clarifier overflow is filtered 
of entrained precipitate and sent to ammonia recovery. The 
underflow is mixed with electrolyte purges from Cu and Ni 
electrowinning as well as the Co recovered from stripping the 
LIX reagent. The mixture is pressure leached with air to prefer- 
entially dissolve the Ni and Co sulfides, leaving the Cu and Zn 
sulfides in the residue. The latter are removed by filtration and 
scid, as minor products, to smelters for recovery of metal 
values. 



Following pH adjustment and reprecipitation with hydrogen 
sulfide for final removal of any Zn and Cu solubilized in the first 
leach, the Ni-Co sulfate solution is heated and autoclaved, 
and Ni is reduced with hydrogen. Sufficient ammonia solution 
is added during reduction to neutralize the acid formed. Only a 
portion of the nickel is removed per pass to prevent overreduction 
and subsequent contamination of the nickel powder with cobalt. 
After densification through repeated recycle, the nickel pow- 
der is removed, washed, and passed to drying and briquetting 
for sale. 

The largely nickel-free cobalt sulfate solution passes to an 
evaporator-crystallizer where the remaining nickel and cobalt 
are precipitated as the double salts with ammonium sulfate. 
Excess ammonium sulfate is purged, and the salts are redis- 
solved in strong ammonia solution. The cobalt in solution is 
oxidized to the cobaltic state (Co^*) with air to allow cobalt to 
remain in solution. The stream is acidified to remove the nickel 
salts that are separated and recycled to the pH adjustment 
step. The nickel-free solution is then heated and autoclaved 
for removal of cobalt by hydrogen reduction. Sufficient ammo- 
nia is added to neutralize the acid generated. The cobalt 
powder is dried and briquetted for sale, and the ammonium 
sulfate is purged to ammonia recovery. 



AMMONIA RECOVERY (FIG. C-1 4) 

The raffinate from cobalt recovery, containing process ammo- 
nium sulfate and ammonia, is countercurrently contacted with 
slaked lime in a boil to recover the ammonia value of the 
sulfate. The precipitate from the lime boil enters a thickener, 
then overflows to the waste surge tank for disposal in a tailings 
pond. The overflow liquor is recycled to the CCD circuit. Steam 
sparged into the lime boil strips ammonia, which passes to a 
three-stage ammonia condenser-absorber circuit. The aque- 
ous absorbed ammonia solution returns to the process. The 
vent gases of the entire process are passed through ammonia 
recovery. Unabsorbed vent gas is discharged to the stack for 
disposal. 



PLANT SERVICES 

Plant services include process and cooling water supply 
and treatment, steam raising and power generation, and stack 
gas treatment. Makeup water is clarified and softened for 
distribution to the process, as required. Additional treatment is 
required for cooling tower water makeup, boiler feed water 
makeup, and for supplying plant potable water. Offgas hydro- 
gen from cobalt recovery along with coal is burned in the 
main boilers to raise the required process steam and generate 
a portion of the power required in the process. Following 
particulate removal, the flue gases are combined with other 
process offgases and pass to gas treatment, where sulfur 
oxides and other acidic constituents are removed by scrub- 
bing with limestone. The scrubbed offgases are reheated (to 
avoid condensation of vapors), combined with scrubbed vents 
from ammonia recovery, and are passed to stacks for disposal. 



MANGANESE PRODUCTION ADD-ON 

The recovery of manganese from H2SO4 leach tails is an 
option that has been investigated. Recovery of manganese 
from the tailings would require dissolution of the residue and 
chemical manipulation to precipitate manganese as an oxide, 



47 



possibly MnOa, involving several separation-purification steps. 
The Mn02 could be used directly in steel production if specifica- 
tions are met.or possibly could be used as a feed material to 
produce ferromanganese or other manganese alloys. The 
recovery of manganese from the process tails would be contin- 
gent on market conditions and process economics. Because 
of the relatively new technology required in manganese recov- 
ery from H2SO4 leach tails, and the dependency on economic 
and technical conditions, no detailed flowsheets are presented 
for this process. 



PROCESS ALTERNATIVES 

A major alternative to the proposed process configuration 
involves a low-temperature and low-pressure treatment of 
slurried nodules in acid solution. There are, however, major 
drawbacks, such as solubilization of an undesirable amount of 
Fe that would need to be removed, longer treatment time, and 
lower recovery of Ni, Cu, and Co. 

Other than the metals separation and purification steps, the 
process configuration is based on the Moa Bay, Cuba, process, 
formerly operated by the Freeport Nickel Co., of New Orleans, 
La. In the absence of actual operating data, there is little 
reason to believe that nickel recovery from ocean floor nod- 
ules will differ significantly from nickel recovery in Moa Bay 
iron-laterite ores. 

A slurry, whether produced from nodules or latente ore, 
when leached at high temperature will substantially extract 
the metals of interest as well as undesirable trace metals in 
amounts depending on the source.The leach reactors are very 
fundamental in design and of proven operational reliability. 



The special alloy flash-down values used in this process are 
economically and mechanically feasible and present the most 
convenient arrangement. 

The Cu raffinate neutralization step, which assumes the use 
of enough ammonia to generate a basic solution and oxidation 
of Co to prevent coextraction with Ni, could be eliminated if a 
reagent could be found to selectively remove Ni in the pres- 
ence of Co. The precipitation and separation of basic salts of 
Fe, Mn, Mg, and Al would be eliminated, with a savings of 
necessary equipment. 

The ammonium sulfate solutions purged from the LIX extrac- 
tion and the copper raffinate neutralization have been treated 
with lime for the recovery of ammonia for recycle. An alternative 
approach would involve direct recovery of ammonia sulfate by 
evaporation-crystallization for sale as a byproduct. The alter- 
native is highly energy intensive because of the number of 
crystallizing-evaporating steps necessary to produce a rela- 
tively pure byproduct from a stream containing many entrained 
process impurities. The production of ammonium sulfate is 
outside the interest of the process and could be severe on the 
local market, because this production would be approximately 
15 pet of present U.S. production and could affect market 
prices. 

Alternative configurations of the metals separation steps 
are possible, such as selective extraction-selective stripping, 
but their impact on overall plant material and energy balances 
should be minor. Many variations are possible in the details of 
the scheme used for recovery of cobalt from a mixed sulfide 
precipitate. The impact on plant requirements would not differ 
appreciably from the present approach, because the sulfides 
will still be oxidized to sulfates, purged, and hydrogen reduced. 
It does not appear likely that the solution could be purified 
easily enough to permit recovery of electrolytic cobalt. 



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APPENDIX D.— REDUCTION AND HCI LEACH PROCESS 



The reduction and HCI leach process is a four-metal pro- 
cess in which Mn, Cu, Ni, and Co are liberated from dried 
nodules by a high-temperature (500° C) gaseous hydrogen 
chloride treatment of nodules. Hydrogen chloride reduces 
manganese dioxide to manganous chloride (liberating chlorine 
gas) and also reacts with other metal oxides to form soluble 
chloride salts. A hydrolysis reaction and quench follow, where 
water is sprayed on the nodules and the iron is precipitated as 
ferric hydroxide. The nodules are leached with water and HCI, 
forming a concentrated pregnant liquor of chloride salts. 

Copper is extracted by liquid ion exchange (LIX) reagents 
from the pregnant liquor, and is stripped and recovered as 
electrowon cathodes. Cobalt is solvent-extracted from the 
copper raffinate, stripped, and separated by precipitation with 
hydrogen sulfide. It is recovered from the sulfide precipitate, 
along with some Ni, Zn, and Cu, by selective leaching and 
hydrogen reduction. Nickel is extracted by LIX reagents from 
the cobalt raffinate, stripped, and recovered as electrowon 
cathodes. The nickel raffinate is evaporated, crystallizing man- 
ganese chloride as well as the other remaining chloride salts. 

The salts are dried using combustion gases in a countercur- 
rent dryer. The dried salts are charged to a high-temperature 
fused salts electrolysis furnace, where molten manganese 
metal is tapped and cast as product and chlorine gas is liberated. 
Excess hydrogen chloride gas in the process is recovered and 
recycled. Generated chlorine gas is recovered, dried, and 
delivered to a local chemical complex which, in exchange, 
returns makeup hydrogen chloride to the process. 

Detailed descriptions of each segment of the process are 
given for the following flowsheets. A summary of operating 
parameters for each section is given in table D-1 . A key to the 
flowsheet symbols is given in figure D-1 . 



ORE PROCESSING AND DRYING (FIG.D-2) 

Wet nodules are reclaimed from storage and fed through a 
primary cage mill where they are reduced to minus 7/8 in. 
They then pass to a fluid-bed dryer where surface and pore 
water is removed at 175° C by direct contact drying with 
combustion gases. Bed overflow is reduced to minus 65 mesh 
in a secondary cage mill, and dryer and mill fines are removed 
from offgases by cyclones and an electrostatic precipitator. 
Offgases pass to gas treatment for scrubbing, while dried 
nodules are transferred hot in an enclosed conveyor to reduction. 



HYDROCHLORINATION (FIG. D-3) 

Dried nodules are reacted in a fluidized bed hydrochlorination 
reactor by contact with the hydrogen chloride gas from the HCI 
surge, which is preheated to 1 75° C. The exothermic reactions 
maintain the reactor at 500° C. Manganese dioxide is reduced 
to manganous chloride, and chlorine is produced. Essentially 
all the Cu, Ni, and Co, as well as 90 pet of the alkali and 
alkaline earths present in the nodules, react to form chloride 
salts. Approximately 100 pet excess HCI gas is used in the 
reaction. This HCI gas, as well as the chlorine and water 
liberated in the reaction are returned to HCI-CI2 recovery. The 
reduced-chlorinated nodules are delivered to a second fluid- 
ized bed where any iron chloride is hydrolyzed by a water- 
spray quench, forming insoluble ferric hydroxide, and the nodules 
are cooled to 200° C. The offgases from both fluidized beds 



are sent to a electrostatic precipitator system for dust removal. 
The hydrolysis offgas is also passed through a waste heat 
recovery system. 



LEACHING AND WASHING (FIG. D-4) 

The chlorinated nodules are leached with water and HCI in a 
tank where the soluble chlorides are dissolved to form a liquor 
with a pH of 2. The solution is cooled to 40° C by circulating the 
liquor through an external heat exchanger. The slurried nod- 
ules are washed countercurrently in a six-stage thickener 
circuit to remove 98 pet of all soluble metal values, forming a 
pregnant liquor. The wash water is recycled water from proc- 
ess water surge. Washed tailings are sent to the waste 
treatment area. Flocculant is added to the thickeners to improve 
the settling properties of the solids. 



COPPER LIQUID ION EXCHANGE (FIG. D-5) 

Pregnant liquor is filtered and passed to a three-stage coun- 
tercurrent LIX extraction circuit where copper is removed from 
pregnant liquor. Some of the other chloride salts are physically 
entrained in the organic phase. These entrained chlorides are 
removed by washing with a water solution in a two-stage wash 
circuit. A purge from this wash solution is returned to the 
pregnant liquor surge, and makeup water is added to the 
circuit equal to this purge. 

The copper is stripped from the organic by countercurrent 
contact in two stages at controlled pH with depleted electrolyte 
from copper electrowinning. Because electrowinning conven- 
tionally occurs at a higher temperature than the operation of 
the LIX circuit, the sthp solution is heated passing to electro- 
winning and cooled passing from electrowinning. 

Provision is made for periodically cleaning the mixer-settler 
units used in extraction and stripping and for recovering organic 
and aqueous phases for recycle. Degraded organic, dust, and 
other forms of "crud" are removed from the organic and 
incinerated. 

Because a small amount of cobalt is coextracted and is not 
stripped with the copper, it must be removed from the LIX 
reagent to prevent its buildup. This is accomplished by precipi- 
tating the cobalt from a purge stream of organic with hydrogen 
sulfide. The precipitated solids are washed from the organic 
and passed to cobalt recovery, while the purified organic is 
returned to the extraction loop. Makeup organic is added to the 
stripped reagent to offset degradation and soluble organic 
losses to pregnant liquor and water wash, and the metal-free 
organic is recycled to extraction. 



COPPER ELECTROWINNING— 
COMMERCIAL (FIG. D-6) 

Cathode copper is recovered from the strong electrolyte 
from LIX using conventional technology. Starter sheets depos- 
ited on titanium blanks from strong electrolyte are removed, 
washed, looped, and returned to the commercial section as 
starters. Full-term cathodes produced in the commercial sec- 
tion are washed, unloaded, and prepared for shipment to sale. 
The major part of the weak electrolyte is recycled to the LIX 
section for stripping 



63 



Table D-1.— Operating parameters for reduction and HCi ieach process 



Parameter ar>d unit 




Value J 


Parameter and unit 






Value 


ORE PROCESSING AND DRYING (FIG. D-2) | 


pH ADJUSTMENT AND COBALT EXTRACTION (FIG. D-7)— Con. 


Feed rate, wet basis (330 days/yr; 24 hr/day) .... 


tpd.. 


3,640 


Metals extraction, pet— Con. 








Feed size to reduction 


mesh.. 


-65 


Mn 






10 


Drying temperature 


"C. 


150 


Ni 
Zn 
Co stnpping 
Stnpping solution pH 









HYDROCHLORINATION (FIG. D-3) | 




Temperature 


°C.. 


500 


4 


Pressure 


atm.. 


1 


Number of stages 






2 


Reagent 




HCI 


Organic-aqueous ratio 






5:1 


Reactions: 






Stnpping, pet 








MnOz + 4 HCI — > MnCl2 +2H2O + Ct 






Co 






99 


FejOa +6HCI-> 2FeCl3 + 3H20 






Mn 






99 


CuO + 2HCI— > CUCI2 H-HaO 






Co recovery 








NiO + 2HCI — > NiClz + HjO 






Precipitating agent 






H2S 


COzOa + 6HCI —> 2C0CI2 + SHjO + CI2 






Precipitation 




pet 


100 








Temperature 




°C 


80 


Temperature 


'C. 

atm 


200 
1 


Pressure 




...atm.. 


1 


Pressure 
HydrochlonnatKXi, pet 
Co 


NICKEL LIQUID ION EXCHANGE (FIG. D-8) 




100 


Extraction: 








Cu 




96 


Extractant 






'KelexlOO 


Fe 




27 


Number of stages 






2 


Mn 




94 


Organic-aqueous ratio 






2:1 


Mo 




96 


Temperature 




°C 


40 


Ni 




100 


Metals extraction, pet 
Ni 
Co 
Cu 








LEACHING AND WASHING (FIG D-4) | 


99.5 
99.5 


RnalpH 




2 


99.5 


Underflow density 


pet solids 


15 


pH (with NaOH) 






4 


Wash ratio 




2:1 


Washing 








Number of stages 




6 


Washing agent 






H2O 


Soluble metals removed 


pet- 


98 








2 




Stripping: 
Strip solution composition, gpl: 
H2S04 








COPPER LIQUID ION EXCHANGE (FIG. D-5) | 




Extraction: 




1 






40 


Extractant 


'KelexlOO 1 


Ni 






50 


Cu feed- 


gpl 


*8 


Number of stages 






2 


Number of stages 




3 


Organic-aqueous ratio 






6:1 






2:1 


Ni stripping 




pet 


99 


Cu extraction 
Washing: 
w&sn composftion 


pet 


99.5 
H2O 


NICKEL ELECTROWINNING-COMMERCIAL (FIG. D-9) 


Current density 




A/m^.. 


180 


Number of stages 




2 


Current effiaency 




pet.. 


93 


Organic-aqueous ratio 




3:1 


Temperature 




°C.. 


60 


Temperature 


°C 


40 


Ni in-out 




gpl- 


75-50 


Metals extraction, pet 






H2SO4 in-out 




gpi- 


0.016-40 


Co 




99.5 


Na2SO« 




gpi- 


100 


Cu 




99.5 
99.5 


HaBOa 




gpi- 


15 


pH (with NaOH) 


MANGANESE RECOVERY (FIG. D-10) 


Stripping: 






Trace elements removal agent 






H2S 


Stnp solution composition, gpl: 






Evaporation-crysfallization water removal 




....pct.. 


99.9 


H2SO«.. 




160 


Fused salt electrolysis: 








Cu 




40 


Mn recovery.... 




pet.. 


90 


Number of stages 




2 


Temperature, metal 




»C.. 


1,300 


Organic-aqueous ratio 




4:1 


Temperature, salt 




°C.. 


800 


Cu stripping 


pet 


95 


Cun-ent density 




A/m^.. 


46 


Temperature 


•c 


40 


COBALT RECOVERY (FIG 


D-11 


) 




COPPER ELECTROWINNING— COMMERCIAL (FIG D-6) | 


Sluny feed, solids 




pet 


40 


Current density 


A/m^ 


180 


Evaporation-crystallization water removal 




pet 


70 


Cun-ent efficiency 


pet 


94 


Co oxidation 








Temperature 


"C 


50 


Temperature 




"C 


100 


Cu in-out 


gpl 


53-40 


Pressure 




psig 


150 


HjSO* in-out 


gpl 


160-180 


Co reduction 
Temperature 
Pressure 
Reductant 




°C 
psig 




pH ADJUSTMENT AND COBALT EXTRACTION (FIG. D-7) | 


175 
500 


Cu raffinate pH adjustment: 






H2 


pH adjustment agent 





NaOH 


LoficninQ 8QGnt 


.pet HaSO^.. 


70 


Number of stages 
Final pH 




1 
4 


HCI RECOVERY (FIG. D-1 2) 


Co liquid ion exchange extraction 
Extractant 


HC\ Ahsnrhinn annnt 






H2O 
H2SO4 




TIOA 


Gas drying agent 






Number of stages 
Organic-aqueous ratio 




3 
2:1 


WASTE RECOVERY (FIG. D-1 3) 


Metals extraction, pet 














Co 




99 


NHa recovery 




....pet.. 


99 


Cu 




100 











'Reference to specific trade names does not imply endorsement by the Bureau of Mines. 



64 



A small amount of nickel is stripped along with the copper not 
deposited in electrowinning, and must be purged from the 
system. The purged electrolyte passes through purification 
cells where copper is removed by electrowinning to depletion. 
The decopperized electrolyte is sent to cobalt recovery for 
further processing. Makeup acid is used to redissolve scrap 
copper for return to the commercial cells for deposition, and 
sufficient steam, wash water, and makeup water are added to 
the circuit to offset water vaporized or carried off with evolved 
oxygen during electrowinning. 



pH ADJUSTMENT AND COBALT 
EXTRACTION (FIG. D-7) 

The raffinate from copper extraction is adjusted in a surge 
tank to a pH of 4 by the addition of NaOH solution. This stream 
then passes to a two-stage countercurrent solvent extraction 
circuit where cobalt is extracted as a tetrachloro-complex by 
the organic reagent. The preferred organic reagent is a tertiary 
amine such as tri-isooctylamine (TIOA). The cobalt is stripped 
from the organic by countercurrent extraction contact in two 
stages with recycled process water. Because of the high man- 
ganese concentration in the raffinate, a portion of it is extracted 
with the cobalt. The cobalt is separated by addition of hydro- 
gen sulfide, which reacts to form cobalt sulfide precipitate 
which is centrifuged from the liquor and sent to cobalt recovery. 
The liquor, which is basically manganese chloride solution, is 
sent to manganese recovery. 



NICKEL LIQUID ION EXCHANGE (FIG. D-8) 

Nickel is recovered in a manner similar to that used in 
copper extraction. The cobalt-free raffinate passes to a three- 
stage countercurrent LIX extraction circuit where nickel is 
removed from the raffinate. Sodium hydroxide solution is added 
at interstages to keep the pH at 4 to ensure good nickel 
extraction. The loaded organic is washed to remove chloride 
in a two-stage operation. The nickel is stripped from the organic 
by countercurrent contact in two stages with depleted electro- 
lyte from nickel electrowinning. Because electrowinning con- 
ventionally occurs at a higher temperature than the LIX circuit, 
the strip solution is heated-cooled passing to-from electrowinning. 

Provisions are also made for cleaning the mixer-settler units 
and sending the resultant "crud" to incineration. An organic 
purge is also taken to ensure against buildup of unstrippable 
metals in the organic. Makeup organic is added to the stripped 
reagent to offset degradation and soluble organic losses. 



NICKEL ELECTROWINNING— 
COMMERCIAL (FIG. D-9) 

Nickel is recovered from the strong electrolyte by electrowin- 
ning in a manner similar to that used for copper recovery. In 
nickel electrowinning, however, cathode bags are used, and 
sodium sulfate and boric acid are added to the electrolyte to 
control its conductivity and pH. Dissolved organic carried from 
the LIX step is removed by adsorption on activated carbon 
prior to any electrolyte passing to electrowinning. Also, the 
starter sheets are pickled in H2SO4 prior to use in the commer- 
cial cells, and nickel scrap is redissolved in HCI-containing 
raffinate and the solution recycled to the cobalt-free raffinate 
surge. The electrolyte purge, required to remove impurities 
from the electrowinning circuit, passes to a sulfide precipita- 



tion reactor and then to cobalt recovery for retrieval of metal 
values. 



MANGANESE RECOVERY (FIG. D-10) 

The raffinate from nickel extraction is combined with the 
wash from cobalt extraction, and these are reacted with hydro- 
gen sulfide to precipitate any remaining metal values that may 
have passed through the series of extractions. These precipi- 
tates are sent to cobalt recovery. The resultant solution is 
evaporated in a triple-effect evaporator using steam as the 
initial heat source. The overhead water is cooled and sent to 
the process water surge for recycle. The wet crystallized chlo- 
ride salts are sent to a dryer, where the salts are passed 
countercurrently with combustion gases to drive off the remain- 
ing surface water as well as any water of hydration. The vent 
from the dryer is sent to gas treatment. The dried salts are 
conveyed in covered systems to a surge, which is blanketed 
with inert nitrogen gas to prevent reabsorption of water. 

From this surge, the salts are fed to a high-temperature 
(1 ,300° C) fused-salt electrolysis furnace where molten manga- 
nese forms and collects at the bottom of the reactor. The 
manganese is tapped periodically and cast into molds and 
sold as metal product. Chlorine gas that evolves from the 
electrolytic reaction is collected, cooled by a water quench, 
and sent to HCI-CI2 recovery. Fused salts are also tapped from 
the reactor. These salts are mold cooled and sent to the waste 
disposal area. A certain amount of the manganese that does 
not pass inspection is recycled to the furnace with additives 
that assist in carrying out a complete recovery of the manganese. 
The lining of the reactor is cooled to prolong its life in this harsh 
environment. Areas surrounding the furnace are hooded, and 
constant venting is maintained to collect fugitive fumes from 
the furnace and the products tapped from the furnace. The 
graphite anode is also continuously replaced. 



COBALT RECOVERY (FIG. D-11) 

Several streams are merged to form the input to the cobalt 
recovery scheme. These are the slurry from Co extraction, 
purge from Mn recovery, the purges from Cu and Ni 
electrowinning, and the solids from organic stripping in Cu and 
Ni extraction circuits. The mixture is pressure leached with air 
to preferentially dissolve the Ni and Co sulfides, leaving the Cu 
and Zn sulfides in the residues. The latter are removed by 
filtration and sold, as minor products, to smelters for recovery 
of metal values. 

Following pH adjustment and reprecipitation with hydrogen 
sulfide for final removal of any Zn and Cu solubilized in the first 
leach, the Ni-Co sulfate solution is heated and autoclaved, 
and Ni reduced with hydrogen. Sufficient ammonia solution 
is added during reduction to neutralize the acid formed. Only 
a portion of the nickel is removed per pass, to prevent 
overreduction and subsequent contamination of the nickel 
powder with cobalt. After densification through repeated recycle, 
the nickel powder is removed, washed, and passed to drying 
and briquetting for sale. 

The largely nickel-free cobalt sulfate solution passes to an 
evaporator-crystallizer where the remaining nickel and cobalt 
are precipitated as the double salts with ammonium sulfate. 
Excess ammonium sulfate is purged, and the salts are redis- 
solved in strong ammonia solution. The cobalt in solution is 
oxidized to the cobaltic state (Co^^) with air. This permits the 
cobalt to remain in solution when the stream is acidified to 



remove the nickel salts, which are then separated and recycled 
to the pH adjustment step. The nickel-free solution is then 
heated and autoclaved for removal of cobalt by hydrogen 
reduction. Sufficient ammonia is added to neutralize the acid 
generated. The cobalt powder is dried and briquetted for sale, 
and the ammonium sulfate is purged to the lime boil. 



HCI RECOVERY (FIG. D-12) 

The offgas from the hydrochlorination reactor contains a 
mixture of unreacted HCI, chlorine, and water. The HCI is 
absorbed by water, forming a highly concentrated aqueous 
HCI solution. The overhead gas from the tower is combined 
with the offgas from electrolysis and is dried by passing through 
a H2SO4 solution, which strongly absorbs the water from the 
gas, leaving dry chlonne for delivery as product. The HCI gas 
from the hydrolysis reactor is absorbed in the second tower, 
producing strong HCI solution. The offgas from this tower is 
mainly humid air and is sent to gas treatment. In both absorp- 
tion towers, the dissolution of HCI is highly exothermic, and the 
heat is removed with cooling water. 

A series of lean HCI vents is scrubbed to remove the last 
remaining HCI in a third tower. The overhead gas from this 
tower is also sent to gas treatment. All the HCI solutions are 
combined with H2SO4, and the HCI is stripped and sent to a 
HCI surge, where makeup HCI is added. The HCI is then sent 
to the hydrochlorination reactor. The bottoms from the HCI 
stripper are sent to a water stripper, where water is taken 
overhead and condensed. The remaining H2SO4 is filtered to 
remove any particulate matter that may have been entrained 
in the gas streams entering the HCI recovery section. The 
resulting strong H2SO4 is recycled. An aqueous HCI stream is 
split from the main aqueous HCI stream to provide acid streams 
needed at various stages in the process. Excess water devel- 
oped in HCI recovery is returned to the process water surge. 



WASTE RECOVERY (FIG. D-13) 

Ammonia is recovered from the ammonia sulfate purges 
from cobalt recovery by reaction with slaked lime. Steam is 
blown into the mixture to strip the evolved ammonia. The 
vapor is combined with other ammonia vents, and they are 
scrubbed with water to form an aqueous ammonia solution 
that is returned to the aqueous ammonia storage for recycle 
within the process. The gypsum slurry from the lime boil is 
cooled and combined with the slurry from stack gas treatment. 
After liquid-solid separation in a thickener, the solids are com- 
bined with other process solid and liquid wastes and plant 
runoff, treated for pH control as required, and pumped to the 
tailings impoundment area for disposal. The overflow from the 
thickener is returned to the process water surge, where it is 
combined with other water returns and makeup water to sat- 
isfy the process water needs. 



PLANT SERVICES 

Plant services include process and cooling water supply 



and treatment, steam raising and power generation, stack gas 
treatment, and combustion gas preparation. Makeup water is 
clarified and softened for distribution to the process, as 
required. Additional treatment is required for cooling tower 
water makeup, boiler feed water makeup, and for supplying 
plant potable water. Process combustible wastes are burned 
along with coal in the main boilers to raise the required proc- 
ess steam and generate a portion of the power required in the 
process. Following particulate removal, the flue gases are 
combined with other process offgases and pass to gas treatment, 
where sulfur oxides and other acidic constituents are removed 
by scrubbing with limestone. The scrubbed offgases are com- 
bined with scrubbed vents from ammonia recovery and are 
passed to stacks for disposal. 



PROCESS ALTERNATIVES 

While data on the reduction of nodules with HCI and subse- 
quent recovery of metal values from acid chloride solution 
have been reported in the patent literature, this technology 
currently has no direct analog in commercial extractive 
metallurgy. Also, while the thermodynamics of the reduction 
step are well known, and reports on laboratory studies of some 
separations of metals from chloride solutions are available, no 
data exist to indicate the expected properties of the nodule 
residues (e.g., filtering rates) or the problems associated with 
recovering a salable manganese metal from impure chloride 
solutions. Thus, the proposed process configuration has been 
established based on literature data that contain little detailed 
engineering and design information and without the benefit of 
insights that might be gained from analogies to conventional 
technology in related operations. This means that alternative 
process configurations might well be technically and economi- 
cally more attractive, but access to more data would be required 
to make such a judgment. 

A major process alternative is to use a low-temperature 
aqueous reduction and HCI leach. The stoichiometry of the 
reactions would consume the same amount of HCI as the 
high-temperature gaseous reduction. However, the iron would 
be dissolved as ferric chloride and would necessitate more 
expensive solvent extraction steps to remove the iron before 
recovering the valuable metals products and a spray roast of 
the resulting iron chloride solution to recover the HCI. On the 
positive side,an aqueous process would not require the drying 
step. 

A number of possible alternatives is available for recovering 
manganese. Direct electrowinning of manganese has been 
proposed, but it is questionable that the final pregnant liquor 
would be pure enough to develop a good electrowon product. 
A cementation on aluminum to obtain manganese has also 
been proposed. The resulting aluminum would be spray roasted 
to recover HCI and form AI2O3 as a product, which must be 
sold or disposed. In addition, the manganese product may be 
contaminated with aluminum. Other schemes propose produc- 
ing manganese hydroxide as a product which, in effect, side- 
steps the problem of obtaining a pure metal product. 

A number of metal separation schemes are possible. These 
include using different organic reagents as solvent extractants 
or LIX reagents. 



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APPENDIX E.— SMELTING AND H2SO4 LEACH PROCESS 



The smelting and H2SO4 leach process is a combination 
pyrometallurgical and hydrometallurgical treatment of nod- 
ules to recover the value metals Ni, Cu, and Co, with the option 
of recovering ferromanganese or a storable byproduct of Mn 
and Fe. The smelting process produces a slag, from which 
ferromanganese is recovered, and a metal alloy matte com- 
posed primarily of Ni, Cu, Co, and S. 

The matte is granulated, slurried, and selectively leached 
with H2SO4 at elevated temperature and pressure. The leach 
residue and metalliferous solution are separated by a series of 
filtering and washing stages. After liquid-solid separation, cop- 
per and nickel are selectively extracted by liquid ion exchange 
(LIX) reagents, stripped from the ion exchange liquid into a 
weak electrolyte, and recovered as electrowon cathodes. Cobalt 
is separated from the raffinate by precipitation with hydrogen 
sulfide and recovered from the sulfide precipitate, along with 
some Ni, Cu, and Zn, by selective leaching and hydrogen 
reduction. Ammonia consumed in the process is recovered by 
lime boil and recycled to the process for use in pH control. 

Detailed descriptions of each segment of the process are 
given for the following flowsheets. A summary of operating 
parameters for each section is given in table E-1 . A key to the 
flowsheet symbols is given in figure E-1. 



ORE PREPARATION AND 
DRYING (FIG. E-2) 

Wet nodules are reclaimed from storage and fed through a 
primary cage mill, where they are reduced to minus % in. They 
then pass to a feed bin for delivery by a feed belt supplying 
nodules to a direct heated, fluid-bed drier for water removal. 



REDUCTION 
(FIG. E-3) 

The dried nodules are combined with coke, and the mixture 
is fed to a fluid-bed roaster for reduction with producer gas. 
After the roaster reduction, cyclones remove and return large 
particulates, while fine dust and hot gases pass to waste heat 
recovery and electrostatic precipitation. The reduced dust is 
delivered back to the process to recombine with the reduced 
products of the roaster. The reduction products are blanketed 
by an inert gas (such as nitrogen) and delivered by hoppers to 
the smelting furnace. 



SMELTING 
(FIG. E-4) 

Reduced nodules, comprised of MnO, FeO, asmall amount 
of metallic Fe, the value metals Ni, Cu, and Co, and the less 
volatile components of nodules, are smelted with silica flux at 
about 1 ,425° C. An electric furnace of conventional design 
would be used. 

Recoveries of Fe, Ni, Cu, and Co are in the range of 70 to 95 
pet along with minor amounts of Mn. The iron alloy is subse- 
quently removed and recycled to the smelting furnace as a 
molten silicate. The slag is comprised mainly of Mn, Fe, and 
Si02-Ca in the proper ratio for good slag fluidity and for subse- 
quent production of ferromanganese. 



CONVERTING (FIG. E-5) 

Manganese reduction in the alloy is held at a level not 
exceeding 2.0 pet because it must be removed to less than 0. 1 
pet prior to reacting the Ni, Cu, and Co with S. Removal of the 
manganese and some iron is accomplished by addition of 
quartzite in the proper ratio to produce an eutectic mixture of 
the low-melting silicates. Oxidation of iron and manganese 
with 95 pet O2 conserves heat for subsequent processing. 

After the Fe-Mn-Si02 slag is removed as a first step, a near 
stoichiometric amount of S must be reacted to form Ni3S2, 
CU2S, and CogSe. These sulfides are stable with respect to Fe 
and FeO at 1 ,200° to 1 ,400° C. The objective is to remove as 
much iron as possible without a major loss of the value metals 
to the exhaust gas or slag. Gypsum, reduced with coke, sup- 
plies the sulfur, and a fuel oil-oxygen burner supplies the heat 
for the reaction. 

A top-blown rotary converter (TBRC) was selected for con- 
verter operations to provide intimate slag-metal-gas contact. 
All of the converting could be done in the same vessel, but two 
are shown in the flowsheet to assist visualization of the four- 
step process. 

The third step is to add silica flux and blow the matte-iron 
alloy with air until the proper amount of iron is removed to 
balance its requirements in the ferromanganese alloy that is 
produced in another section of the plant. Alternatively, if iron in 
the nodules were low enough in relation to manganese, all of 
the iron silicate slag could be recycled to smelting. 

As a final converting step, iron is lowered to 5 pet by a series 
of alternate blowing-slag removal-fluxing-blowing operations. 
The reaction is highly exothermic, requiring some care in 
prevention of Fe304 production. 

The finished matte contains about 90 pet of the Ni, Cu, and 
Co and is removed by ladle to granulation. 



FERROMANGANESE 
REDUCTION (FIG. E-6) 

Ferromanganese can be produced from the smelter slag in 
an open air electric furnace with a reductant. Coke or several 
other carbonaceous materials would be suitable as reductants. 

The reduction reaction requires intensive energy input from 
the electric arc. Because the charge is primarily molten, the 
bath surface will be exposed in molten form. Standard ferro- 
manganese production is from cold ore, and a crust is present 
on the bath surface. 

Medium carbon ferromanganese is produced, and a slag 
containing about 8 pet manganese is discarded as the final 
waste product from the hot metal operations. 



MATTE LEACHING (FIG. E-7) 

The molten alloy from converting is quenched in a granula- 
tion unit. The granulated alloy is rake classified, with oversize 
granules going to wet milling for final size reduction while 
classifier fines overflow to a clarifier, where they are settler 
thickened. The clarifier underflow recombines with wet mill 
effluent in a surge tank, while overflow returns to granulation. 
The matte slurry is pumped to an autoclave leaching vessel 
operated at 1 50 psig and 110° C. The leach products, die- 



80 



Table E-1.— Operating parameters for smelting and H2SO4 leach process 



Parameter arxj unit 




™. 1 


Parameter and unit 


Value 


ORE PREPARATION AND DRYING (FIG. E-2) | 


FERROMANGANESE REDUCTION (FIG. E-6)— Con. 


Feed rate, wet tMSis (330 days/yr; 24 hr/day 

Feed size 


tpd.. 

in.. 

°C.. 


10.900 
-7/8 
150 


Slag composition, pet 

CaO 
MnO 
NaaO 
MgO 




Drying temperature 




15 


REDUCTION (FIG. E-3) | 


22 
8 


Reduction gas: 
Producer gas 




..pet CO.. 
pet coke.. 


S20 
»4.5 

90 
90 
100 
100 
20 
90 

725 
925 


4 
3 










MATTE LEACHING (FIG. E-7) 




Reduction reactions: 


+ C02 

O + CO2 
CO^ 

J02 

COj 

to + 3CO2 




MnOz + CO— > MnO 
Fe203 + CO->2Fe 
CuO + CO— > Cu + 
NiO + C0— >Ni + C 
CoO + CO— >Co + 
M0203 + 3CO— >2*/ 
Metals reduction, pet: 
Co 
Cu 


Matte temperature ° C 
Granulation temperature, initial ° C 

Output partde size mesh 
Pulp density pet 
Leaching 

Temperature ° C 

Pressure psig 

Time hr 

Leachate 
Recovery, pet 

Co. 

Cu. 

Fe. 

Mn. 

Ni.. 
Washing effiaeney pet 
Filtration stages 


1.325 

95 

Ball mill 

-325 

9.5 

110 

150 

2 


Fe 

Mn 
Mo 
Ni 
Temperature. ° C 
Solids 




H2S04 

99 
99 
99 
80 


Gas 





99 


SMELTING (FIG. E-4) | 


98 
2 






°C *1,325 

hr 2 

Silica 

Co)<e, electrodes 

90 
90 
70 
2 
85 
95 

<10 
<10 
20 
98 
15 
<10 






Temperature 


pH ADJUSTMENT (FIG. E-8) 




Retention time 






Rux 

Reductant 

Alloy recovery, pet 


Agent 

H3SO«in-out 

SdkJs removal method 


CaC03 

5-0.5 

Clarifier 






Cu 


COPPER LIQUID ION EXCHANGE (FIG. E-9) 


Fe 
Mn 
Mo 
Ni 




Extraction: 

Extractant 

Number of stages 


'LIX 64N 

3 

6:1 


Slag recovery, pet 
Co 


Metals extraction, pet: 

Ni 

pH (controlled by NH3) 





Cu 
Fe 
Mn 




100 



25 


Mo 

Ni 




Temperature °C.. 

Stripping: 
Strip solution composition, gpl: 

HzSO* 

Cu 
Number of stages 
Organic-aqueous ratio 
Stnpping, pet 

Co 

Cu 

Ni 

Zn 


40 


CONVERTING (FIG. E-5) 


160 


Slagging: 
Rux 
Oxidant 
Removal, pet 
Fe 
Mn 
Final Mn 
Converting and blowing 


ure 


pet 
pet 

"C 


Silica 
O^-air 

12 
93 
0.1 

Silica 
83 

90 
90 

5 

<.1 
90 
1,400 


40 

2 

2:1 

0.2 
87 

.9 
100 


nux 


COPPER ELECTROWINNING-COMMERCIAL (FIG. E-11) 


Final alloy (matte) 
Recovery, pet 
Co 
Cu 
Fe 


Current density A/m^.. 

Cun'ent efficiency pet.. 

Temperature "C. 

Cuin-out gpl.. 

H2S04in-out gpl.. 


180 

94 

50 

53-40 

160-180 


Ni 


COPPER RAFFINATE NEUTRALIZATION (FIG. E-1 2) 


Slag discharge temperat 


Agent NH 

Final pH 


3 with air 




lANGANESE REDUCTION (FIG. E-6) 






FERROW 


Solid removal method Filtr. 


ition with 


Furnace type 




Electric arc 
Coke, producer 
gas, electrodes 

7 
14 
78 


filter aid 


Reduetants 


NICKEL LIQUID ION EXCHANGE-EXTRACTION (FIG. E-1 3) 


Alloy composition, pet 

c 

Fe 
Mn 
Si 


Extraction: 
Extractant.. 
Number of stages 
Organic-aqueous ratio 


'LIX 64N 

3 

7:1 



'Reference to specific trade names does not imply endorsement by the Bureau of Mines. 



81 



Table E-1. — Operating parameters for smelting and H2SO4 leach process — Continued 



Parameter and unit 



Parameter and unit 
COBALT RECOVERY (FIG. E-1 6)— Con. 

Metals precipitated, pet: 

Co 

Cu 

Nl 

Zn 

Temperature °C.. 

Clarifier underflow: 

Density pet solids.. 

Wash ratio 

Leaehing: 

Slurry density pot solids.. 

Agent pctHzSO*.. 

Evaporation-crystallization water removal pet.. 

Co oxidation: 

Temperature °C.. 

Pressure psig.. 

Co reduction: 

Temperature °C.. 

Pressure psig.. 

Reduetant 

AMMONIA RECOVERY (FIG. E-1 7) 

NH3 recovery pet.. 

Temperature "C. 

Underflow density pet solids.. 

NHa stripping: 

Pressure atm.. 

Recovery pet.. 

Number of stages 

Direct condensation: 

Temperature °C.. 

Pressure atm.. 

Number of stages 

NH3 absorber: 

Temperature °C.. 

Pressure atm.. 

Number of stages 



NICKEL LIQUID ION EXCHANGE-EXTRACTION (FIG. E-1 3)— Con. 



Extraction — Con. 

Co 

Cu 



Ni 

Temperature 

Ammonia wash (primary): 

Washing agent pet I 

Number of stages 

Organic-aqueous ratio 



NICKEL LIQUID ION EXCHANGE-STRIPPING (FIG, E-1 4) 



Ammonia wash (secondary): 
Scrub solution, gpl: 

H2S04 

(NH4)2S04 

Number of stages 

Organic-aqueous ratio... 
Stripping: 

Number of stages 

Organic-aqueous ratio 

Stripping, pet: 

Co 

Cu 

Ni 



NICKEL ELECTROWINNING— COMMERCIAL (FIG. E-15) 



Current density 
Current efficiency 
Temperature 
Ni in-out.. 
H2SO4 in-out 
Na2S04... 
H3BO3 



99.5 
40 



200 
2 

1:1 



0.3 
<.004 




COBALT RECOVERY (FIG. E-1 6) 



Precipitating agent.. 



.pet NH4HS.. 



98 

99.9 

99 



5 
2:1 

40 
70 
70 

100 
150 

175 
500 
H, 



solved value metals and residue, are combined with other 
precipitated solids and fed to a two-stage countercurrent rotary 
drum filter-repulp operation. The filtered solids are pumped to 
waste treatment while the filtrate, which is now process preg- 
nant liquor, is pumped to a pH adjustment circuit prior to 
selective metal removal. 



pH ADJUSTMENT (FIG. E-8) 



electrolyte is heated on passage to electrowinning and cooled 
on passage from electrowinning to permit operation of electro- 
winning at a higher temperature. Makeup organic is added to 
the electrolyte-stripped reagent to offset degradation and solu- 
ble organic losses to pregnant liquor. A continuous purge to 
and recycle from a trace metal stripping step is operated to 
prevent a buildup of impurities (fig. E-10). The aqueous raffi- 
nate stream containing the nickel, cobalt, and trace metal 
values is sent to a neutralizing step prior to nickel recovery. 



The pH adjustment process removes the necessary resid- 
ual acid concentration of the pregnant liquor through the use of 
calcium carbonate (limestone). The precipitate (calcium sulfate) 
is removed by a clarifier, filtered, and the overflow is pumped 
to the copper LIX circuit. 



COPPER LIQUID ION 
EXCHANGE (FIG. E-9) 

The filtered pregnant liquor from pH adjustment passes to a 
three-stage countercurrent LIX circuit with interstage pH 
adjustment. Nearly complete transfer of Cu metal to the organic 
exchange liquid is accomplished along with trace exchanges 
of the Ni, Co, and Zn. The separated and loaded organic 
stream is countercurrently stripped of its copper value with 
depleted electrolyte from copper electrowinning. The copper 



COPPER ELECTROWINNING— COMMERCIAL 
(FIG. E-1 1) 

Cathode copper is recovered from the LIX strong electrolyte 
using conventional technology. Starter sheets of copper are 
deposited on titanium blanks, and are removed, washed, looped, 
and returned to the commercial section. Full-term cathodes 
produced in the commercial section are washed, unloaded, 
and prepared for shipment to sale. The major portion of the 
weak electrolyte is recycled to the LIX section for stripping, 
while a small purge stream is recycled to the pH adjustment 
process to prevent buildup of undesirable co-stripped metals 
other than copper. Makeup acid, used to redissolve scrap 
copper for return to the commercial cells for deposition, replen- 
ishes the weak electrolyte (a strong acid solution) for return to 
copper stripping. Sufficient steam, wash water, and makeup 



82 



water are added to the circuit to offset water vaporized and 
carried off with evolved oxygen during electrowinning. 



COPPER RAFFINATE NEUTRALIZATION (FIG. 12) 

The Ni-bearing solution from the Cu ion exchange process 
contains an excess of acid, which must be neutralized and 
made slightly basic with ammonia and oxidized before the Ni 
values can be removed without coextraction of Co. In addition 
to neutralization, tank aeration causes precipitation of the Fe, 
Mn, Mg, and Al initially extracted from the matte and carried 
with the raffinate. 

The collected precipitated solids are sent to disposal. The 
pH adjusted filtrate containing some entrained precipitate passes 
on to nickel LIX. 



NICKEL LIQUID ION EXCHANGE-EXTRACTION 
(FIG. E-13) 

The neutralized raffinate is filtered of entrained precipitate, 
then nickel is separated in three stages of pH-controlled coun- 
tercurrent extraction with an organic ion exchange extractant. 
Other trace metals and ammonia are exchanged along with 
the nickel. The nickel-stripped raffinate containing primarily 
cobalt is sent to cobalt separation. Entrained aqueous solution 
and dissolved ammonia are removed from the organic phase. 
The entrained aqueous solution is removed in a physical 
liquid-liquid separation step. The ammonia is partially removed 
in a two-stage countercurrent aqueous wash of organic fol- 
lowed by steam stripping of the ammonia. The organic phase 
is then sent to nickel stripping. 



NICKEL LIQUID ION EXCHANGE-STRIPPING 
(FIG. E-14) 

The partially ammonia-stripped organic passes to a second 
stage for reaction with sulfuric acid to draw the remaining 
ammonia into an aqueous phase. The phases are countercur- 
rently contacted and separated in two stages. The aqueous 
phase returns to nickel extraction. The organic phase, contain- 
ing nickel and trace metal impurities, enters two countercur- 
rent stages of nickel stripping with weak electrolyte from 
electrowinning. This electrolyte is-heated-cooled in going to-from 
the electrowinning operation, which is operated at a slightly 
higher temperature than stripping. The nickel-free organic is 
replenished of losses with fresh organic. A small amount of 
organic is purged to a trace metals removal step to prevent 
impurity buildup. The "cleaned" organic purge and makeup 
organic are combined with the nickel-free organic for recycle 
to the nickel ion exchange extraction step. 

NICKEL ELECTROWINNING— COMMERCIAL 
(FIG. E-15) 

Nickel is recovered from the strong electrolyte by electrowin- 
ning in a manner similar to that used for copper recovery. In 
the nickel electrowinning, however, cathode bags are used, 
and the strong electrolyte is chemically conditioned with sodium 
sulfate and boric acid to control conductivity and pH. Dis- 
solved organic, carried from the LIX step, is adsorbed in an 
activated carbon bed prior to any electrolyte passing to 
electrowinning. The bed is periodically isolated from the sys- 
tem and steam stripped of organic. Nickel is recovered in a 



manner similar to that used for copper recovery. The starter 
sheets are pickled in H2SO4 prior to use in the commercial 
cells, and nickel scrap is redissolved in ammonia-containing 
raffinate and recycled to the ion exchange process. The elec- 
trolyte purge required to remove impurities from the electrowin- 
ning circuit passes to raffinate neutralization. The strongly 
acidic, depleted electrolyte returns to the nickel stripping circuit. 



COBALT RECOVERY (FIG. E-16) 

Along with unextracted Cu, Ni, and Zn, Co is recovered from 
the Ni LIX raffinate by precipitation with ammonium hydrosul- 
fide (produced by sparging hydrogen sulfide into an excess of 
ammonia solution). The sulfide precipitate is separated from 
the raffinate in a clarifier. The clarifier overflow is filtered of 
entrained precipitate and sent to ammonia recovery. The under- 
flow is mixed with electrolyte purges from Cu and Ni electrowin- 
ning as well as the Co recovered from stripping of the LIX 
reagent. The mixture is pressure leached with air to preferen- 
tially dissolve the Ni and Co sulfides, leaving Cu and Zn 
sulfides in the residue. The latter are removed by filtration and 
sold as minor products to smelters for recovery of metal values. 

Following pH adjustment and reprecipitation with hydrogen 
sulfide for final removal of any Zn and Cu solubilized in the first 
leach, the Ni-Co sulfate solution is heated and autoclaved, 
and Ni reduced with hydrogen. Sufficient ammonia solution is 
added during reduction to neutralize the acid formed. Only a 
portion of the nickel is removed per pass to prevent overreduction 
and subsequent contamination of the nickel powder with cobalt. 
After densification through repeated recycle, the nickel pow- 
der is removed, washed, and passed to drying and briquetting 
for sale. 

The largely nickel-free cobalt sulfate solution passes to an 
evaporator-crystallizer where the remaining nickel and cobalt 
are precipitated as the double salts with ammonium sulfate. 
Excess ammonium sulfate is purged, and the salts are redis- 
solved in a strong ammonia solution. The cobalt is oxidized to 
the cobaltic state (Co^*) with air to enable cobalt to remain in 
solution. The stream is subsequently acidified to remove the 
nickel salts that are separated and recycled to the pH adjust- 
ment step. The nickel-free solution is then heated and auto- 
claved for removal of cobalt by hydrogen reduction. Sufficient 
ammonia is added to neutralize the acid generated. The cobalt 
powder is dried and briquetted for sale, and the ammonium 
sulfate is purged to ammonia recovery. 

AMMONIA RECOVERY (FIG. E-17) 

The raffinate from cobalt recovery, containing process ammo- 
nium sulfate and ammonia, is countercurrently contacted with 
slaked lime in a steam strip or boil step to recover the ammonia 
value of the sulfate. The gypsum precipitate from the lime boil 
enters a settler, then underflows to the waste surge tank for 
disposal. The overflow liquor is recycled to the granulation- 
leach-washing circuit. Steam sparged into the lime boil strips 
ammonia, which then passes to a three-stage ammonia 
condenser-absorber circuit. The aqueous absorbed ammonia 
solution returns to the process at required locations. The 
ammonia-containing vent gases of the process are passed 
through ammonia recovery. Scrubbed vent gas is discharged 
to the stack for disposal. 



WASTE TREATMENT 

Molten waste slag from ferromanganese production and 



83 



converting is granulated by spraying it with large quantities of 
process waste water and makeup water, with heat removed by 
evaporation. Gases from smelting and converting pass through 
electrostatic precipitators for dust removal. Reducing and sulfur- 
containing gases are directed to the main boilers for combus- 
tion and subsequent cleaning; clean gases are scrubbed directly. 
Process dusts are conditioned by wetting and agglomerating 
with lime. Sulfurous dusts are recycled to the sulf idizing converter, 
while other dusts are returned to smelting and/or purged, as 
required, to control the buildup of heavy metals in the ferroman- 
ganese product. All process solid and liquid effluents are 
collected, neutralized, and pumped to the waste disposal area. 



PLANT SERVICES 

Plant services include process and cooling water supply 
and treatment, steam raising and power generation, stack gas 
treatment, and producer and dryer gas production. Makeup 
water is clarified and softened for distribution to the process, 
as required. Additional treatment is required for cooling tower 
water makeup, boiler feed water makeup, and supplying plant 
potable water. Offgas hydrogen from cobalt recovery and 
offgases from reduction and smelting steps are burned in the 
main boiler, along with coal, to raise the required process 
steam and generate a portion of the power required in the 
process. Following particulate removal, the flue gases are 
combined with other process offgases and pass to gas treatment, 
where sulfur oxides and other acidic constitutents are removed 
by scrubbing with limestone. The scrubbed offgases are 
reheated, combined with scrubbed vents from various proc- 
ess steps, and passed to stacks for disposal. 

Gas for nodules reduction is produced in a two-stage entrained 
flow gasifier in which coal is mixed with preheated air and 
high-temperature steam for the production of a cartwn monoxide- 
rich reducing gas. The gasifier product passes directly to 
reduction following particulate removal and energy recovery, 
with sulfur removal from this and other boiler flue gases taking 
place after combustion. Coal is also used in production of hot 
combustion gas for nodule drying. 



PROCESS ALTERNATIVES 

The processing scheme proposed for the recovery of metal 
values from nodules has been based on a very limited amount 
of published data on nodule properties and behavior under 
smelting-converting conditions. The matte processing 
(hydrometallurgical) operations would be essentially the same 
as those used in direct high-temperature acid leaching of the 
nodules. 

At the present time, the only known production of matte from 
lateritic nickel ore is carried out directly in low-shaft blast 
furnaces, followed by converting. Societe M^tallurgique le 
Nickel employs a blast furnace on New Caledonian laterites. 
The conventional process requires gypsum and coke in the 
burden to supply the sulfur, while sodium sulfate is used for 
this purpose in Japan. A preliminary step of nodule smelting to 
an alloy is necessary, because manganese oxide preferen- 
tially reacts with sulfur. Electric furnace smelting of laterites is 
widely practiced, but the product is ferronickel instead of matte. 
Manganese nodules, however, contain too much copper and 
cobalt to yield a marketable ferroalloy product, and must be 
further upgraded by mechanical or hydrometallurgical methods. 

The drying, reduction, and smelting steps could be more 
thermally efficient (independent of waste heat boiler 



considerations) if the hot reduction offgases were used for 
nodule drying. Circular grates, grate kilns, and other counter- 
current contactors have been designed to combine the drying- 
reduction step, but only the blast (shaft) furnace concept is 
known to combine the reduction with smelting. Fluid-bed dryers 
and reduction or calcination roasters are generally state-of- 
the-art choices. 

Alternate types of converter designs should meet the objec- 
tive of high Ni, Cu, and Co recovery from matte containing less 
than 5 pet Fe. Pierce-Smith (P-S) converters of various designs 
are more widely used than TBRC's, but the TBRC is a suitable 
replacement. 

Pyrite is often used to sulfidize laterites and could be used to 
sulfidize nodule smelting alloy. A total of 95 tpd of pyrite would 
be required to replace 265 tpd of gypsum, if equal sulfur 
utilizations were possible, and energy requirements would be 
reduced. However, it is possible that sulfur utilization could be 
poorer, which would impose an added burden on the gas- 
cleaning system. 

A possible option for recovery of metals from matte would 
be the HCI leaching process used by Falconbridge Nikkelverk 
AS in Nonway. Nickel is preferentially dissolved with HCI, then 
iron and cobalt are solvent extracted. Nickel chloride is hydro- 
lyzed after HCI is stripped, and nickel oxide is marketed. 
Copper is recovered from the matte residue by sulfation roast- 
ing and electrowinning. Cobalt recovery is similar to the pro- 
cess selected in this appendix. 

Another possible method of matte upgrading is practiced by 
INCO. The process depends upon cooling a matte at a slow 
rate so that alloy phases separate from a sulfur matte. The 
alloy is then recovered by crushing and a magnetic separation- 
flotation cycle. Recovery by this method is of the order of 50 
pet and requires recycle of the matte. 

While a number of options was considered for recovering 
the metals from matte, the chosen route involves a H2SO4 
leach with oxidation of the sulfides, followed by conventional 
LIX and electrowinning. This option has been implemented in 
essence by Outokumpu Oy and AMAX on copper-nickel matte 
from conventional ores. 

The Cu raffinate neutralization step, which assumes the use 
of enough ammonia to generate a basic solution and oxidation 
of Co to prevent coextraction with Ni, could be eliminated if a 
reagent could be found to selectively remove Ni in the pres- 
ence of Co. The precipitation-separation of basic salts of Fe, 
Mn, Mg, and Al would be eliminated with a saving of necessary 
equipment. 

In the selected flow scheme, the ammonium sulfate solu- 
tions purged from the LIX extraction and the copper raffinate 
neutralization have been treated with lime for the recovery of 
ammonia for recycle. An alternative approach would involve 
direct recovery of ammonium sulfate by evaporation- 
crystallization for sale as a byproduct. The alternative is highly 
energy intensive because of the number of crystallizing- 
evaporating steps necessary to produce a relatively pure 
byproduct from a stream containing many entrained process 
impurities. 

Alternative configurations of the metals separation steps 
are possible, such as selective extraction-selective stripping, 
but their impact on overall plant material and energy balances 
should be minor. Many variations are possible in the details of 
the scheme used for recovery of cobalt from a mixed sulfide 
precipitate. The impact on plant requirements would not differ 
appreciably from the present approach because the sulfides 
will still be oxidized to sulfates, purged, and hydrogen reduced. 
It does not appear likely that the solution could be purified 
easily enough to permit recovery of electrolytic cobalt. 



84 



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